FUNDAMENTAL ANATOMICAL AND

PHYSIOLOGICAL S'IUDIES ON THE

FEATHER RELEASE MECHANISM IN
THE DOMESTIC FOWL ,

Thai: for ”MB mod PI D

MICHIGAN STATE UNIVERSITY
Orville William Ostmann
1962 ’

IHEESIS

This is to certify that the
thesis entitled
FUNDAMENTAL ANATOMICAL AND PHYSIOLOGICAL STUDIES ON THE

FEATHER RELEASE MECHANISM IN THE DOMESTIC FOWL

presented by

Orvi 1 1e Wi lliam Os tmann

has been accepted towards fulfillment
I of the requirements for

Mdegree in Poultrv Science

I
V 1

Major professor

 

en, .93“;

Date November 16, 1962

 

0-169

LIBRARY

Michigan State
University

 

 

 

FUNDAMENTAL ANATOMICAL AND PHYSIOLOGICAL STUDIES ON THE

FEATHER RELEASE MECHANISM IN THE DOMESTIC FOWL

BY

Orville William Ostmann

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Department of Poultry Science

1962

.’,,.
Yér’/?

ABSTRACT

FUNDAMENTAL ANATOMICAL AND PHYSIOLOGICAL STUDIES ON THE
FEATHER RELEASE MECHANISM IN THE DOMESTIC FOWL

by Orville William Ostmann

The present method by which feathers are removed from
poultry is unsatisfactory from the standpoint of quality of
the product produced and efficiency of processing. Develop—
ment of new, more efficient methods of removing feathers,
however, is severely handicapped by a lack of knowledge of
the forces that hold the feather in its follicle, as well as
the physiological mechanism(s) by which these forces can be
controlled. Therefore, the purpose of this investigation
was to ascertain basic information regarding feather release
and tightening in poultry. The investigation consisted of
two general studies, namely, anatomical and physiological.

In the anatomical investigation, gross and microscopic
studies were conducted. For the purpose of making the gross
study, skin from the dorsal feather tract of a cooked turkey
was used. The microscopic studies were, for the most part,
made on tissues taken from the back region of chickens,

although tissues from the leg, neck and breast were also

ABSTRACT

FUNDAMENTAL ANATOMICAL AND PHYSIOLOGICAL STUDIES ON THE
FEATHER RELEASE MECHANISM IN THE DOMESTIC FOWL

by Orville William Ostmann

The present method by which feathers are removed from
poultry is unsatisfactory from the standpoint of quality of
the product produced and efficiency of processing. Develop—
ment of new, more efficient methods of removing feathers,
however, is severely handicapped by a lack of knowledge of
the forces that hold the feather in its follicle, as well as
the physiological mechanism(s) by which these forces can be
controlled. Therefore, the purpose of this investigation
was to ascertain basic information regarding feather release
and tightening in poultry. The investigation consisted of
two general studies, namely, anatomical and physiological.

In the anatomical investigation, gross and microscopic
studies were conducted. For the purpose of making the gross
study, skin from the dorsal feather tract of a cooked turkey
was used. The microscopic studies were, for the most part,
made on tissues taken from the back region of chickens,

although tissues from the leg, neck and breast were also

Orville William Ostmann

studied. Tissues were taken from chickens in the anesthe-
tized, unanesthetized and molting state. Various methods of
processing and staining were used.

The feather follicle is a tubular structure that is
dilated into an onion shaped area called the bulb. Attached
to the bulb area of the follicle are various bundles of
smooth muscle fibers. These fibers radiate from the folli—
cle in many directions, but generally course from the area
of the dermal papilla to the apex of an adjacent follicle.
Thus, a unique criss-cross pattern is formed. The muscles
attach to the follicle by tendons which are replete with
elastic fibers. These fibers continue, in conjunction with
connective tissue, around the follicle and in so doing, form
the outermost layer of the follicular wall.

The muscles of the feather follicle are richly supplied
with nerve fibers which terminate in free nerve endings.
These fibers apparently contain both motor and sensory fibers
and, based on physiological studies, are both sympathetic
and parasympathetic in origin. Numerous sensory end—organs,
Vater Pacini corpuscles, were observed in close association
with the feather follicle.

No apparent histological differences were observed in

Orville William Ostmann

skin taken from anesthetized and unanesthetized birds. This
was attributed to the fact that skin removed from an anes—
thetized bird underwent changes which allowed the feathers

to return to their tightened state before fixation occurred.
Skin taken from birds subjected to scalding was too distorted
for any detailed histological analysis to be made.

In the physiological study, a series of experiments were
conducted to evaluate the effect of 1) brain sticking; 2)
various classes of drugs; 3) spinal transection; and 4)
skeletal muscles on feather release in chickens. Feather
pulling force, as measured with a spring scale, was used as
the criterion.

In the brain sticking studies feather loosening occurred
when the stick was made into the diencephalon-cerebellum or
the medulla—cerebellum. Due to the procedure used in making
the stick, none of these parts were pierced alone; conse—
quently, the exact part of the brain involved could not be
determined. When the cerebrum or optic lobes were pierced,
feather loosening failed to occur.

Drugs which were effective in reducing feather pulling

force were sodium pentobarbital, chloroform, ether, procaine

(anesthetics); chlorpromazine, promazine (tranquilizers);

Orville William Ostmann

atropine (parasympatholytic); and yohimbine (sympatholytic).
All of the neuromimetic drugs, acetylcholine, pilocarpine,
carbachol (parasympathomimetic); epinephrine and ephedrine
(sympathomimetic), failed to significantly alter the force
required to pull an individual feather from its follicle.
All levels of spinal transection significantly reduced
feather pulling force of feathers pulled from the dorsal
feather tract posterior to the level of the transection.
Feather pulling force of feathers pulled anterior to the
level of the transection remained relatively unchanged.
Skeletal muscles apparently do not function in the
release of the feather from its follicle. This was indi-
cated when curare, a skeletal muscle depressant, failed to

reduce the force required for feather removal.

ACKNOWLEDGMENTS

The author wishes to express his sincere appreciation
to Dr. R. K. Ringer, Associate Professor of Poultry Science,
for his guidance, understanding and patience throughout this
graduate program, and for his helpful suggestions and assis-
tance in the preparation of this manuscript.

Sincere gratitude is expressed to Dr. H. C. Zindel,
Chairman of the Department of Poultry Science, for provi-
sion of the facilities and materials necessary to carry out
this study. The author is indebted to Dr. Theo H. Coleman,
Associate Professor of Poultry Science, for his helpful
suggestions and constructive review of this manuscript.
Thanks are also due to the United States Department of Agri—
culture for the grant which made this study possible.

Special gratitude is extended to Mrs. Marjorie Tetzlaff
for the preparation of the histological sections and to
Ronald Peterson for cooperation and assistance in collect—
ing the data.

Above all, I am unable to express adequately my grate-
fulness to my wife, Harriet, for her interest, patience,

understanding and unending encouragement during this strenuous

ii

period of graduate study and research. The sacrifices and
understanding of my children, Belinda and Julie, are also

recognized and appreciated.

iii

 

TABLE OF CONTENTS

Page
I Acknowledgment . . . . . . . . . . . . . . . . . ii
II Table of contents . . . . . . . . . . . . . . . iv
III List of tables . . . . . . . . . . . . . . . . . v
IV List of figures . . . . . . . . . . . . . . . . viii
V Introduction . . . . . . . . . . . . . . . . . . 1
VI Review of literature . . . . . . . . . . . . . . 3
A. The anatomy of the feather follicle and its
immediate surroundings . . . . . . . . . . . 3
B. Factors influencing the release of the
feather from its follicle . . . . . . . . . 6
VII Objectives . . . . . . . . . . . . . . . . . . . 18
VIII Experimental procedure . . . . . . . . . . . . . 19
A. General . . . . . . . . . . . . . . . . . . 19
l. Anatomical studies . . . . . . . . . . . l9
2. Physiological studies . . . . . . . . . 23
3. Statistics . . . . . . . . . . . . . . . 28
B. Specific techniques . . . . . . . . . . . . 28
l. Anatomical studies . . . . . . . . . . . 28
IX Experimental results . . . . . . . . . . . . . . 32
A. Anatomical studies . . . . . . . . . . . . . 32
B. Physiological studies . . . . . . . . . . . 70

iv

XI

XII

1. Experiment I. Effect of piercing
various parts of the brain on feather
pulling force . . . . . . . . . . . . .
2. Experiment II. Effect of neuromimetic,
anesthetic and tranquilizing drugs and
drugs which depress the autonomic
nervous system on feather pulling force.
3. Experiment III. Effect of spinal
transection on feather pulling force
4. Experiment IV. Effect of skeletal
muscles on feather pulling force . . .
General discussion . . . . . . . . . . . . .
A. Anatomical studies . . .
B. Physiological studies . . . . .

Summary and conclusions . . . . . . . . . .

Literature Cited 0 O O O 0 U 0 O O 0 O 0 O O U 0

Page

70

76
86
94
102
102
110
117

122

 

LIST OF TABLES

Table

l Feather pulling force of feathers pulled from

excised skin of anesthetized White Leghorn

hens O O O O O O O O O O 0 6' O Q

2 Effect of piercing various parts of the brain

0 O O O O

on feather pulling force of feathers pulled
from the dorsal feather tract of chickens .

3 Effect of anesthetics on feather pulling force
of feathers pulled from the dorsal feather tract
of chickens . . . . . . . . . .

4 Effect of a single intravenous injection of

chlorpromazine or promazine on feather pulling

force of feathers pulled from the dorsal

feather tract of chickens . . .

5 Effect of neuromimetic drugs on feather pulling

force of feathers pulled from the dorsal

feather tract of chickens . .

6 Effect of drugs which depress the activity of
the autonomic nerves on feather pulling force

of feathers pulled from the dorsal feather

tract of chickens . . . . .

7 Effect of spinal transection at

0 6 0

the thoracic

level on feather pulling force of feathers

pulled from the dorsal, femoral
feather tracts of White Leghorn

8 Effect of spinal transection at
sacral level on feather pulling
feathers pulled from the dorsal
feather tracts of White Leghorn

9 Effect of spinal transection at
sacral level on feather pulling

feathers pulled from the femoral tract of White

Leghorn hens . . . . . . . .

vi

and pectoral
hens

the lumbar-
force of
and pectoral
hens

the lumbar-
force of

(J (a O 0 Q 0

Page

66

74

82

83

84

85

95

96

97

 

Table

10

11

12

Page

Feather pulling force of feathers pulled from

the dorsal feather tract of White Leghorn hens

before and after death by bleeding or sodium
pentobarbital . . . . . . . . . . . . . . . . . 98

Effect of a single intravenous injection of

curare on feather pulling force of feathers

pulled from the dorsal feather tract of White

Leghorn hens . . . . . . . . . . . . . . . . . . 100

Effect of spinal transection at the thoracic

level on feather pulling force of feathers

pulled from the dorsal feather tract of a White
Leghorn hen . . . . . . . . . . . . . . . . . . 115

vii

Figure

LIST OF FIGURES

Application of the spring scale used to
measure feather pulling force . . . . . . . .

Photomicrograph of skin taken from the dorsal
feather tract of a turkey showing the general
view of the muscular arrangement between five
feather follicles . . . . . . . . . . . . .

Photomicrograph of a longitudinal section of
skin taken from the dorsal feather tract of a
chicken showing the criss—cross pattern of
muscles as they course between adjacent
feather follicles . . . . . . . . . . . . .

Photomicrograph of a dissected feather follicle
from the dorsal feather tract of a turkey

Photomicrograph of a longitudinal section of
skin taken from the dorsal feather tract of a
chicken showing a feather follicle containing

a mature feather, two feather follicles con-
taining immature feathers and the complexity of
the muscles involved . . . . . . . . . . . . .

Photomicrograph of a longitudinal section of
skin taken from the dorsal feather tract of a
chicken showing a cross section of a mature
feather follicle and its surroundings . . .

Photomicrograph of a cross section of skin
taken from the dorsal feather tract of a
chicken showing the keratinized epithelium of
the feather follicle as being continuous with
the keratinized epithelium of the skin

Photomicrograph of a longitudinal section of

skin taken from the dorsal feather tract of

a chicken showing the microscopic bridges of
adherence between the keratinized calamus and
the keratinized layer of epithelium

viii

Page

25

33

36

38

41

43

46

48

Figure

LIST OF FIGURES

Application of the spring scale used to
measure feather pulling force . . .

Photomicrograph of skin taken from the dorsal
feather tract of a turkey showing the general
view of the muscular arrangement between five
feather follicles . . . . . . .

Photomicrograph of a longitudinal section of
skin taken from the dorsal feather tract of a
chicken showing the criss—cross pattern of
muscles as they course between adjacent
feather follicles . . . . . . . . .

Photomicrograph of a dissected feather follicle

from the dorsal feather tract of a turkey

Photomicrograph of a longitudinal section of
skin taken from the dorsal feather tract of a
chicken showing a feather follicle containing
a mature feather, two feather follicles con-

taining immature feathers and the complexity of

the muscles involved . . . . . . . . . . .

Photomicrograph of a longitudinal section of
skin taken from the dorsal feather tract of a
chicken showing a cross section of a mature
feather follicle and its surroundings . . .

Photomicrograph of a cross section of skin
taken from the dorsal feather tract of a
chicken showing the keratinized epithelium of
the feather follicle as being continuous with
the keratinized epithelium of the skin

Photomicrograph of a longitudinal section of
skin taken from the dorsal feather tract of

a chicken showing the microscopic bridges of
adherence between the keratinized calamus and
the keratinized layer of epithelium

viii

0

Page

25

33

36

38

41

43

46

48

Figure

10

ll

12

13

14

Photomicrograph
skin taken from
chicken showing

of a longitudinal section of
the dorsal feather tract of a
the attachment of smooth mus-

cles to a follicle containing an immature
feather by tendons . . . . . . . .

Photomicrograph
skin taken from
chicken showing
relation to the

Photomicrograph
skin taken from
chicken showing

of a longitudinal section of
the dorsal feather tract of a
the Vater-Pacini corpuscle in
feather follicle . . . . . .

of a longitudinal section of
the dorsal feather tract of a
a nerve trunk coursing through

the connective tissue stroma . . . . . . . .

Photomicrograph

of a longitudinal section of

muscular tissue present in skin taken from the
dorsal feather tract of a chicken showing the
involvement of the nervous system . . . . .

Photomicrograph

of a typical cholinesterase

reaction of muscle present in skin taken from
the dorsal feather tract of a chicken . .

Photomicrograph
skin taken from

of a longitudinal section of
the dorsal feather tract of a

chicken following scalding . . . . . . . . .

ix

9

Page

51

53

56

58

61

64

 

INTRODUCTION

The method by which feathers are removed during process—
ing is one of the factors that affects final appearance,
tenderness and keeping quality of the carcass, as well as
processing efficiency. As it is well known, there are several
methods by which the feathers may be removed. Commercially,
however, the method that is unanimously employed is the
”scald—pick“ method. This method is based upon the fact that
heat from the water denatures proteins which are present in
the muscle of the feather follicle, thus allowing muscular
relaxation and feather release.

During the past fifteen years, optimum scald water tem—
perature has been the subject of considerable research. Al—
though considerable progress has been made, the most advanced
method of feather removal still falls short of the goal of
producing, with minimum labor, a clean, completely feather-
free carcass having a stable, attractive skin surface.

Development of new, more efficient methods of removing
feathers, however, is seriously handicapped by a lack of
knowledge of the forces that hold the feather in its folli-
cle, as well as the physiological mechanisms by which these

forces can be controlled.

The general objective of this investigation has been to
ascertain a basic understanding of the physiological mech-
anisms involved in the release of the feather from its

follicle.

REVIEW OF LITERATURE
A. The anatomy of the feather follicle and its immediate
surroundings.
A search of the literature reveals very little informa—
tion on the anatomy of the feather follicle and its immedi—
ate surroundings. Most of the information available on this

subject is in regard to the muscles which move the feather

 

and was reported in the nineteenth century. The muscles
of the feather follicle were first described by Nitsch (1840),
who reported that four separate muscles were usually attached
to the follicle of each contour feather. He further reported
that sometimes six and more rarely five were present.
Seuffert (1862) according to Langely (1904) observed
that contour feather follicles of the trunk region usually
had two to four separate muscles. He stated that the mus-
cles were unstriated and attached to the follicle by elastic
tendons. These muscles were observed to course from the
lower part of one follicle to the upper part of an adjacent
follicle. Similar observations were made by Helm (1884)
as cited by Langley (1904).
Langley (1902b) noted that each feather follicle in the

neck region had two sets of muscles, which he named erector

and depressor. He also noted that the number and arrange-
ment of these muscles varied considerably and as many as
sixteen muscular attachments to a single follicle were
observed.

In a subsequent report, Langley (1904) presented a very
detailed description of the muscles which move the feathers.

It was his observation that each feather usually had four

 

 

small unstriated muscles which arise within the dermis.
Many times, however, one or two more were present. The
muscles were of three general types: (1) erector muscles
coursing from the neck of one follicle to the end (bulb) of
the follicle anterior to it; (2) depressor muscles coursing
from the neck of one follicle to the follicle posterior to
it; and (3) retractor muscles coursing from the neck of one
follicle to the neck of an adjacent follicle. He reported
that these muscles were situated anterolaterally, postero-
laterally and longitudinally from the mid—dorsal line.
According to Langley their function was to erect, depress
or retract the feather, respectively.

During the course of the many studies of Lillie and co—
workers on experimental feather development, many photo~

Inicrographs and seni-diagrammatic drawings of the developing

 

feather were presented. From a semi-diagrammatic drawing
which was presented by Lillie (1940) it could be seen that
the follicle was enclosed by a circular muscle. This, in
turn, was bordered by the levator muscle which moves the
feather.

According to Langley (1904) the first information on the

innervation of these muscles was secured by Jegorow in 1890.

 

 

Using the turkey as the experimental bird, Jegorow found
that depression of the head and neck feathers occurred upon
stimulation of the cervical sympathetic nerve. On the other
hand, Langley (1902a) reported that when the cervical sym—
pathetic nerve was severed, feather ruffling occurred in
the peripheral area of the skin which was innervated by the
nerve. In addition, the latter worker reported that follow-
ing transection of the cervical spinal cord, and stimulation
of the lower end, the contour feathers over the entire body
were depressed and drawn closely to the skin. Later,
Langley (1902b) reported that feather ruffling was also under
the control of the sympathetic nervous system.

Further evidence that the sympathetic system is involved
in feather movement was provided by Langley (1904). Using

the chicken and pigeon, he observed that if any part of the

sympathetic system was stimulated, the ordinary effect was
a depression of the feathers. At times, however, a strong
erection of the feathers occurred. This he attributed to
stimuli affecting the spinal cord, as the same effect was
observed when the cord itself was sectioned. Further
evidence suggesting that the cord was involved was brought
forth when strychnine, a spinal cord stimulant, caused
irregular movement of the feathers.
B. Factors influencing the release of the feather from its
follicle.

Influence of scalding on feather release.——The fact that

 

scalding, submerging the bird into water at a controlled
temperature for a given period of time, facilitates feather
removal is well known. However, much of the information
obtained has been on an empirical basis. According to
Benjamin gt a1. (1960) the first method of scalding to be
widely used in commercial processing plants was the hard—
scald. Birds subjected to this method of scalding are sub—
merged for 30—60 seconds in water at a temperature of 160—
18OOF. The ease with which feathers may be removed from
birds processed by this method is well known. It has the

disadvantage of removing the epidermal layer of the skin.

Thus, bacteria may enter and seriously impair the shelf-
life of the bird. Because of this adverse effect, this
method was discarded in favor of the semi- or slack method
of scalding. In this method, the temperature of the water
is 123 to 1300F; the exact temperature depending on the
kind and age of the bird and the length of immersion time.

The temperature of the scald water that is generally used

 

for chickens, and which was shown by Pearse and Lavers (1949)
to result in an optimum quality carcass, is 1280F. These
workers further reported the optimum immersion time to be

40 seconds. Under these conditions, feather removal by
mechanical pickers was found to be incomplete; thus increas-
ing the labor required for pinning and finishing.

The present trend in poultry processing has been toward
the use of higher scald water temperatures of 138-1400F. for
30-75 seconds. This method, commonly called sub-scalding,
was evaluated by Gwin (1950, 1951a, 1951b). He reported
that feather removal was nearly complete by mechanical
pickers, therefore, markedly increasing processing effi-
ciency. He further reported that part of the epidermal
layer of skin was removed and unless the carcass was kept

moist, the flesh darkened. In a subsequent report, Gwin

 

(1952) pointed out that the amount of labor required for
pinning and processing following sub-scalding could be re—
duced as much as 80 percent over lower scald water tem—
peratures (semi-scalding). Similar results were reported
by Pool g: a1. (1954) and Stadelman and Ziegler (1955).
Using an objective measure, Pearse and Lavers (1949)
related feather pulling force to scald water temperature
and length of scalding time. They reported that birds
scalded in water at 1250F. for 30 seconds required 15 ounces
of pulling force to remove an individual feather from its
follicle. In contrast, birds subjected to scald water
temperature of 136OF. for 15 seconds required only 5 ounces.
Pool e3 a1. (1954) conducted an experiment to evaluate
scalding temperatures and time of immersion on feather
removal of turkeys. Individual feather pulling force was
used as the criterion. They found that as the temperature
of the scald water decreased, feather pulling force in—
creased. Moreover, the increase was in a consistent manner
with the decreasing scalding temperatures. When scalding
time was varied from 30 to 120 seconds at a constant scald
water temperature of 125OF., no significant difference in

feather pulling force was noted. Thus, these workers concluded

w—i. ,

m! '

that scalding time is a much less critical factor than scald
water temperature in feather removal. Similar results were

reported by Knapp and Newell (1961) in the chicken. In

addition, the latter workers presented data which demonstrated

that scalding time had a greater effect at scald water tem-
perature of 1280F. than at any other temperature which they
tested. The latter researchers further reported that at
scald water temperature of 1420F., scalding time of 45 sec-
onds gave optimum results.

Recently, reports have appeared in the literature in
which the effects of various factors in combination with
scalding were studied. Knapp and Newell (1961) studied the
combined effects of scald water temperature, scalding time
and length of fasting period (without feed and water) on
feather removal of White Leghorn hens. The birds were
fasted for either 6 or 8 hours, then killed and scalded for
45 or 90 seconds at a temperature of 128, 135 or 1420F.
These researchers reported that fasting did not have any
beneficial effects on feather removal. In live birds, how—
ever, fasting resulted in a slight but insignificant re-
duction in feather pulling force.

Klose t al. (1961) reported on the combined effects of

 

 

10

anesthesia and scalding. They observed that chickens which
were anesthetized with sodium pentobarbital, then scalded
in water at a temperature of 122, 128 or 1400 F. for 60
seconds, had an individual feather pulling force lower than
those birds subjected to either scalding or anesthesia alone.
Furthermore, this effect was observed for all three scald
water temperatures. They suggested, “that the lower (1220
F.) scalding temperature might be acting through a nerve-
muscle relaxing mechanism.”

Although scald water temperature has been the subject
of considerable research, the actual phySiological process
involved in the release of the feather from its follicle by
this method remains unknown. The present theory is that
heat, from the water, denatures proteins which are present
in the muscles of the feather follicle, thus allowing mus-
cular relaxation and feather release (Winters and Funk,
1960; Benjamin gt _l,, 1960). This theory is supported, in-
directly, by the results of Pearse and Lavers (1949), Pool
._§.al. (1954) and Knapp and Newell (1961).

Recent data, presented by Klose §t_al. (1962) further

confirm the theory of denaturation of muscle protein. These

workers reported that feather pulling force was reduced by

 

12

Apparently, the first factual information on the essential
area of the brain involved in feather release was provided
by King (1920). Working with broilers and pigeons, he
reported that none of the brain above the level of the
cerebellum and medulla was required for release of the
feather. In an attempt to isolate which specific part of
the brain was involved, he subjected birds to ether anes-
thesia, which was shown to have no effect upon the feather
muscles; he also removed the skull and stimulated or
destroyed various parts of the brain. In eight out of ten
birds tested, stimulation or damage to the cerebellum
failed to result in feather loosening. On the other hand,
all birds in which only the medulla was involved, exhibited
loose feathers. In View of these results, he concluded that
the center involved in feather release was located in the
medulla.

Weaver (1936), however, indicated that the center in-
volved in feather release was not located in the medulla,
but rather in the anterior portion of the cerebellum. His
conclusion was based on results obtained from studies con-
ducted on exposed brains of birds under chloroform anes—

thesia. It was his contention that feathers loosened by

Thus, bacteria may enter and seriously impair the shelf—
life of the bird. Because of this adverse effect, this
method was discarded in favor of the semi— or slack method
of scalding. In this method, the temperature of the water
is 123 to 1300F; the exact temperature depending on the
kind and age of the bird and the length of immersion time.
The temperature of the scald water that is generally used
for chickens, and which was shown by Pearse and Lavers (1949)
to result in an optimum quality carcass, is 1280F. These
workers further reported the optimum immersion time to be

40 seconds. Under these conditions, feather removal by
mechanical pickers was found to be incomplete; thus increas-
ing the labor required for pinning and finishing.

The present trend in poultry processing has been toward
the use of higher scald water temperatures of 138-14OOF. for
30-75 seconds. This method, commonly called sub-scalding,
was evaluated by Gwin (1950, 1951a, 1951b). He reported
that feather removal was nearly complete by mechanical
pickers, therefore, markedly increasing processing effi-
ciency. He further reported that part of the epidermal
layer of skin was removed and unless the carcass was kept

moist, the flesh darkened. In a subsequent report, Gwin

 

(1952) pointed out that the amount of labor required for
pinning and processing following sub—scalding could be re—
duced as much as 80 percent over lower scald water tem-

peratures (semi-scalding). Similar results were reported

 

by Pool gt_al. (1954) and Stadelman and Ziegler (1955).
Using an objective measure, Pearse and Lavers (1949)

related feather pulling force to scald water temperature

 

and length of scalding time. They reported that birds
scalded in water at 1250F. for 30 seconds required 15 ounces
of pulling force to remove an individual feather from its
follicle. In contrast, birds subjected to scald water
temperature of 136OF. for 15 seconds required only 5 ounces.
Pool §£_al, (1954) conducted an experiment to evaluate
scalding temperatures and time of immersion on feather
removal of turkeys. Individual feather pulling force was
used as the criterion. They found that as the temperature
of the scald water decreased, feather pulling force in-
creased. Moreover, the increase was in a consistent manner
with the decreasing scalding temperatures. When scalding
time was varied from 30 to 120 seconds at a constant scald
water temperature of 1250F., no significant difference in

feather pulling force was noted. Thus, these workers concluded

that scalding time is a much less critical factor than scald
water temperature in feather removal. Similar results were
reported by Knapp and Newell (1961) in the chicken. In
addition, the latter workers presented data which demonstrated
that scalding time had a greater effect at scald water tem-
perature of 1280F. than at any other temperature which they

tested. The latter researchers further reported that at

 

scald water temperature of 1420F., scalding time of 45 sec-
onds gave optimum results.

Recently, reports have appeared in the literature in
which the effects of various factors in combination with
scalding were studied. Knapp and Newell (1961) studied the
combined effects of scald water temperature, scalding time
and length of fasting period (without feed and water) on
feather removal of White Leghorn hens. The birds were
fasted for either 6 or 8 hours, then killed and scalded for
45 or 90 seconds at a temperature of 128, 135 or 1420F.
These researchers reported that fasting did not have any
beneficial effects on feather removal. In live birds, how-
ever, fasting resulted in a slight but insignificant re-
duction in feather pulling force.

Klose 2E.§i° (1961) reported on the combined effects of

 

10

anesthesia and scalding. They observed that chickens which
were anesthetized with sodium pentobarbital, then scalded
in water at a temperature of 122, 128 or 1400 F. for 60
seconds, had an individual feather pulling force lower than
those birds subjected to either scalding or anesthesia alone.
Furthermore, this effect was observed for all three scald
water temperatures. They suggested, "that the lower (1220
F.) scalding temperature might be acting through a nerve—
muscle relaxing mechanism.”

Although scald water temperature has been the subject
of considerable research, the actual phySiological process
involved in the release of the feather from its follicle by
this method remains unknown. The present theory is that
heat, from the water, denatures proteins which are present
in the muscles of the feather follicle, thus allowing mus-
cular relaxation and feather release (Winters and Funk,
1960; Benjamin §E_§l,, 1960). This theory is supported, in-
directly, by the results of Pearse and Lavers (1949), Pool
_t__l, (1954) and Knapp and Newell (1961).

Recent data, presented by Klose spiel. (1962) further

confirm the theory of denaturation of muscle protein. These

workers reported that feather pulling force was reduced by

 

 

10

anesthesia and scalding. They observed that chickens which
were anesthetized with sodium pentobarbital, then scalded

in water at a temperature of 122, 128 or 1400 F. for 60
seconds, had an individual feather pulling force lower than
those birds subjected to either scalding or anesthesia alone.

Furthermore, this effect was observed for all three scald

 

water temperatures. They suggested, “that the lower (1220
F.) scalding temperature might be acting through a nerve-
muscle relaxing mechanism.“

Although scald water temperature has been the subject
of considerable research, the actual phySiological process
involved in the release of the feather from its follicle by
this method remains unknown. The present theory is that
heat, from the water, denatures proteins which are present
in the muscles of the feather follicle, thus allowing mus-
cular relaxation and feather release (Winters and Funk,
1960; Benjamin §t_§l,, 1960). This theory is supported, in-
directly, by the results of Pearse and Lavers (1949), Pool
_t_§l, (1954) and Knapp and Newell (1961).

Recent data, presented by Klose e; a1. (1962) further

confirm the theory of denaturation of muscle protein. These

workers reported that feather pulling force was reduced by

 

11

50—70 percent in birds subjected to radiant heat which was
supplied by either a photo flood lamp or an infra-red lamp.
They further demonstrated that.feather pulling force was
markedly influenced by the type of scalding medium used.
Water was found to be the most effective in loosening the
feathers, followed in decreasing order by propylene glycol
and mineral oil. They suggested that these differences in
effectiveness "could arise from the appreciable difference
in viscosity, wetting ability and specific heat represented
by the three liquids." It was also noted that under—skin
temperature for birds scalded in these three liquids at
126OF. was considerably different. They reported that
within one minute under—skin temperatures increased from
104OF. to ll7OF. for birds scalded in water. In contrast,
birds scalded in mineral oil showed an increase only to
111°F.

Influence of the nervous system on feather release.-—

 

Another factor which is known to influence feather release
is the nervous system, as indicated by feather loosening
when a successful brain stick is performed. Just what
portion of the brain is involved, however, is controversial,

although the medulla is regarded to be the essential part.

 

12

Apparently, the first factual information on the essential
area of the brain involved in feather release was provided
by King (1920). Wbrking with broilers and pigeons, he
reported that none of the brain above the level of the
cerebellum and medulla was required for release of the
feather. In an attempt to isolate which specific part of
the brain was involved, he subjected birds to ether anes-
thesia, which was shown to have no effect upon the feather
muscles; he also removed the skull and stimulated or
destroyed various parts of the brain. In eight out of ten
birds tested, stimulation or damage to the cerebellum
failed to result in feather loosening. On the other hand,
all birds in which only the medulla was involved, exhibited
loose feathers. In view of these results, he concluded that
the center involved in feather release was located in the
medulla.

Weaver (1936), however, indicated that the center in-
volved in feather release was not located in the medulla,
but rather in the anterior portion of the cerebellum. His
conclusion was based on results obtained from studies con-
ducted on exposed brains of birds under chloroform anes-

thesia. It was his contention that feathers loosened by

 

 

13

piercing the center in the cerebellum could be made to
tighten by subsequent piercing of the medulla. In addition,
Weaver stated that two separate and distinct nerves were
associated with the feather muscles; one being responsible
for relaxation of the feathers, the other responsible for
tightening the feathers.

Recently, Klose §t_§l, (1962) presented data which also
indicate that the nervous system is involved in feather
release. They reported that when the brain was pierced by a
blade inserted through the eye socket, feather loosening
occurred within 15—30 seconds. However, the effect lasted
for less than one minute. The area of the brain in which
these sticks were made was not reported.

Electric shock has also been shown to cause feather
release. Rose (1939) reported that satisfactory feather
release could be obtained when the birds were subjected to
450-500 volts of electricity for a period of 10 seconds.
The results were inconsistent and were not quite as good
as those obtained by a successful brain stick. A subjective
measure was used in this study. Satisfactory results were
said to be obtained when the feathers could be plucked with

reasonable ease and without tearing the skin. A metal

 

l4

clamp attached to the head of the bird was used to provide
electrical contact.

The influence of drugs on feather release.-—Unti1 recently,
the effect of drugs on the muscles of the feather follicle
received comparatively little attention. Langley (1904) used
atropine, curari, apocodeine, and supra—renal extracts and
observed no effects upon feather movement. In contrast,
nicotine, injected intravenously, resulted in a strong
depression of the feathers over the entire body. A subsequent
dose, however, had no further effect upon feather movement.
He attributed the depression of feathers to a stimulatory
effect of the drug upon the sympathetic ganglia. He further
reported that strychnine, following morphia and curari,
caused an irregular rhythmic movement of the feathers for
one to two minutes, the movement being an erection and
depression. It was his conclusion that the action of
strychnine appeared to be on the central nervous system as
feather movement of the head and neck failed to occur when
both the cervical sympathetic nerves were cut.

King (1920) studied the effects of several classes of
drugs on the muscles of the feather follicle and/or the

nerve center involved in feather loosening. His results

 

15

indicated that chloroform, atropine, scopolamine, apomor—
phine, strychnine and amyl nitrite loosened the feathers as
much as did the successful brain stick. Drugs which were
tried but found to have no effect on feather loosening were
eserine, adrenalin, morphine, curare, chloral hydrate,
heroin, emetin and camphor.

It has recently been reported that oral administration
of sodium pentobarbital was effective in loosening the
feathers. Huston and May (1961) reported that feather re-°
moval was 90 to 95 percent complete when the anesthetized
birds were plucked dry by commercial machines after death
by bleeding. Klose gt 21. (1962) also studied the effect
of oral administration of sodium pentobarbital on feather
loosening. They, too, reported feather loosening following
anesthetization. However, their data revealed that this
effect could not be carried over into the post mortem state.
Thus, their results are in disagreement with those of Huston
and May (1961).

Intravenous injection of sodium pentobarbital has also
been shown to be effective in causing feather loosening
(Klose g: al., 1961, 1962). In the latter report, data were

presented which indicated that anesthesia reduced feather

l6

pulling force by approximately 70 percent of the value ob—
served in the conscious bird. These workers also presented
data in the latter report on feather pulling force of fowl
which were subjected to a small or massive lethal dose of
sodium pentobarbital. From this study, these workers re-
ported that feather pulling forces of birds subjected to the
small lethal dose returned to 80-100 percent of the pre-
injection level within 1—2 minutes after death. Massive
doses, however, were found to prolong this time.

There is also evidence which indicates that tranquil—
izing drugs may influence further relaxation. Sturkie gt _1.
(1958) reported that tranquilizing doses of reserpine, given
to capons, apparently caused relaxation of the feather
follicle, as indicated by the dropping of feathers when
handled. Observations by Klose £3 a1. (1961) revealed that
reserpine, fed at 50 or 110 ppm for l, 7 or 14 days, reduced
feather pulling force in the live birds. The effect failed
to persist after slaughter. Similar results were reported
when the tranquilizer was administered intravenously. Knapp
and Newell (1961) also observed that oral administration of

reserpine was effective in reducing the force required for

feather removal in the pre-slaughter state. They further

 

17

reported that practically a straight line relationship
existed between the level of the drug and feather pulling
force. In addition, the latter workers also observed that
trifluoperazine was effective in releasing the feather from

its follicle.

OBJECTIVES

The objectives of this investigation were:

1. To characterize the anatomical features of the
feather follicle and its immediate surroundings.

2. To characterize, by histological techniques, the
essential changes involved in feather loosening.

3. To determine the part of the brain which is in-
volved in the release of the feather from its
follicle.

4. To investigate the effect of spinal transection on
the release of the feather from its follicle.

5. To investigate the effects of various synthetic
drugs on the release of the feather from its
follicle.

6. To investigate the role played by skeletal muscle,
if any, in the release of the feather from its

follicle.

18

 

 

EXPERIMENTAL PROCEDURE

A. General.

1. Anatomical studies.——Gross and microscopic obser-

 

vations on the anatomy of the feather follicle and its
immediate surroundings were studied. The macroscopic anatm
omy was studied in skin taken from the dorsal feather tract
of a “cooked” turkey. Before dissection, the tissues were
placed in ethyl ether to extract a portion of the fat. The
dissected tissues were studied with the aid of a dissecting
scope as well as a microscope. Photomicrographs of the
dissected tissues were taken with a Kodak 35 mm Photomicro—
graphic camera.

The microscopic studies were, for the most part, made
on tissues taken from the back region of chickens, although
tissue from the leg, neck and breast were also studied.
Tissues of approximately 10 X 10 mm were taken from birds
in the following physiological states. unanesthetized,
anesthetized and molting. Tissues were also taken from
birds which were subjected to scalding (l4OOF for 1 1/2
minutes). After the tissues were removed from the birds,

the feather quills were cut off just above the dorsal surface

19

 

20

of the skin to facilitate sectioning.

Except as otherwise indicated, the sections were pro—
cessed in an autotechnicon (Model 2A) in the normal manner
(Armed Forces Institute of Pathology, 1957). The tissues
were fixed in either neutral 10 percent formalin, Zenker‘s
fluid or Bouin“s fluid, depending on the type of stain to
be used.

Following processing, the tissues were embedded in
paraffin and cooled rapidly. Paraffin blocks were cut,
trimmed and mounted on a metal object holder. Blocks were
cut on a Spencer Rotary Microtome.

At first, sections were cut at a thickness of 4-6
microns; however, it was found that for detail study of the
feather follicles these sections were inadequate. Thicker
sections were found to be superior; consequently, all sec-
tions, except as otherwise indicated, were cut at 7—10
microns.

The majority of the sections were cross-sections, since
these appeared to give the most information regarding the
relationship of the different skin structures to the feather
follicle. Longitudinal sections were also made, however,

and were especially useful in demonstrating the innervation

 

21

of the muscles of the feather follicles. Only follicles
containing mature feathers were studied.

The sections were floated on a water bath, affixed to
clean slides with Mayer's egg albumen, dried in a paraffin
oven at 560C and deparaffinized. The sections were then
stained by either a general or specific stain, depending
upon the various histological details being studied. For
the study of general histology, the following stains were
employed (Armed Forces Institute of Pathology, 1957; Conn,

Darrow and Emmel, 1960):

l. Harris's hematoxylin and eosin
2. Masson's trichrome stain
3. Gomori's trichrome stain

4. Van Gieson stain for collagen fibers

5. Heidenhain's aniline blue

6. Gallego's iron fuchsin

7. Gomori°s aldehyde fuchsin; metanil yellow counter-

stain

8. Hematoxylin-Shorr S3 stain

In neurological staining. the general histological method
of processing tissue is of little value. This is contributed

to by the fact that a large number of structural peculiarities

 

22

exist in the nervous system. These peculiarities vary

greatly in their reaction to staining. Consequently, spe—

cific techniques have been developed for demonstrating a

specific structure.

In this study, nerves and their endings were of particu—

lar interest. In order that these could be demonstrated,

the following methods were employed:

1.

Chloral Hydrate Silver Method (Conn, Darrow and
Emmel, 1960). Tissues were fixed in chloral hydrate—
alcohol solution for 1—3 days. Following fixation,
the tissues were stained for 5—6 days in 2 percent
aqueous silver nitrate. The tissues were embedded
in paraffin and sectioned on a rotary microtome at
7-10 microns.

Silver Method for Nerve Axoplasm (Winkelmann and
Schmit, 1957). This method is dependent upon the
impregnation of silver into the nervous tissue. The
tissue was fixed several days in 10 percent formalin.
Sections were cut at 50 microns on a freezing micro-
tome and stained with silver nitrate.

Histochemical Method for Cholinesterase (Gomori,

1952). This method is based upon the demonstration

 

23

of an enzyme, cholinesterase, which is found in the
membrane of all cholinergic fibers but is Virtually
absent from the adrenergic fibers. This permits one
to distinguish cholinergic from adrenergic fibers.
Acetyl and butyryl-tricholine were used as substrates.
Elimination of these substrates served as the con-
trol. The tissues were fixed in 10 percent formalin
for 1-4 hours. Sections were cut on a freezing micro-
tome at a thickness of 50-100 microns. The tissues
were not counterstained.

2. Physiological studies

 

Feather pulling force.-—The criterion used in this
part of the investigation was feather pulling force which
may be defined as the force required to pull an individual
feather from its follicle. In order that this force might
be recorded, it became necessary to devise some instrument
which would give accurate results. Earlier workers reported
that a spring scale, with a hemostat attached to hold the
feather, proved to be satisfactory (Pearce and Lavers, 1949;
Pool gt_al., 1954; Klose et al., 1961). A potentiometer was
also reported to give satisfactory results (Knapp and Newell,

1961).

 

24

At first, a balance which measured in grams was used.
Attached to the pan of the balance, via a string passing
over a pulley, was a hemostat. As the bird was pulled from
the scale, the force required to pull the feather was re-
corded. Although this method proved to be accurate, it was
nevertheless cumbersome. Consequently, a spring scale was

employed (Fig. 1). A hemostat was used to attach the scale

 

to the feather. The scale was calibrated from 0 to 32
ounces; however, a conversion factor (1 ounce = 28.4 gms)
was used so that results could be reported in grams. The
spring scale was tested for accuracy against the previously
used balance and was found to be accurate. During the
feather pulling procedure, the scale was held in a manner
such that the line of pull tended to coincide with the angle
in which the feather was imbedded.

During the latter part of these studies a spring scale,
calibrated in 10 gram divisions was used. In addition, this
scale possessed a maximum reading pointer and was very similar
to the one used by Klose _£_al, (1961).

In preliminary work considerable differences in feather
pulling force were found when feathers were pulled from

different areas of the body. The most consistent pull

25

.munom.mCHHH5m Hdfipmom ousmmoe ou poms mamom mcanmm 03p mo COHDMUHHQQ<

.H

.mE

 

 

27

occurred when feathers were pulled from the back area (dor-
sal feather tract). Similar observations were reported by
Klose §£_§l, (1961). Consequently, all results reported,
unless otherwise specified, are from feathers pulled from
the dorsal feather tract. It was also noticed that con-
siderable variation between individual feathers within a
given area existed. Much of this variation was due to the
state of maturity of the feathers involved. Immature
feathers released from their follicles when very little pull
was exerted. Therefore, in order that an accurate feather
pulling force could be recorded, only mature feathers were
used. A mature feather may be defined as one which has a
hard, dry quill and is embedded well into the follicle. Each
feather was examined for its state of maturity before and
after pulling. A minimum of five feathers were pulled for
each observation made, since it was previously demonstrated
that there were no significant differences in feather pulling
force between the first five and second five feathers pulled
from individual birds (Klose g; al., 1961).

Experimental birds.-—The birds used in these experiments
were birds which were previously used in a nutrition and/or

management study, although some cull hens were also utilized.

 

28

Only birds possessing a good set of feathers (non-molting)
were used. White Leghorn hens, which were in good laying
condition, were used in most of the experiment. Some White
Rock hens and broilers were also used, however. In addition,

a few White Leghorn cockerels were used.

3. Statistical analysis.——For statistical analysis, the

 

”t” test was employed (Snedecor, 1955). Each drug was studied
individually at each of the levels and/or methods of adminis-
tration. No comparisons between drug efficacy, with respect
to feather release, were made. The percent change in feather
pulling force at each observation was figured from the value
obtained in the normal state. The data are presented as

the mean value with its standard error.

B. Special techniques.

1. Anatomical studies.—-One of the objectives of the

 

histological studies was to characterize any changes that
occurred between the feather follicle and its surroundings

in the tightened and the relaxed state. During preliminary
observations of tissues taken from birds in the anesthetized
and unanesthetized state, no apparent histological differences

were noted. Thus, it was conceivable that skin, containing

 

 

29

feathers in the relaxed state by virtue of anesthesia,
underwent changes which allowed the feathers to return to
their tightened state before fixation could occur. Subse—
quent physiological studies, which will be discussed later,
substantiated the above fact. It was Obvious, therefore,
that in order to observe the feather follicle and its sur-
roundings in the relaxed state induced by anesthesia, his—
tological techniques other than those of the standard method
must be used. Consequently, the techniques of freeze-
drying and frozen—sections were employed.

Freeze drying technique.--A relatively inexpensive freeze-
drying apparatus was used. The apparatus consisted of a
vacuum pump with a hose attached to a vacuum flask which,
in turn, was immersed in a beaker containing a solution of
alcohol and dry ice. Insulation was then placed around the
beaker containing the alcohol—dry ice solution. A thick
wall Florence Flask was attached to an outlet of the vacuum
flask, for the purpose of containing the tissue.

Tissues were taken from White Leghorn males in the un=
anesthetized or anesthetized state and subjected to one of
the following treatments: 1) placed directly in the drying

flask attachment; 2) frozen immediately by placing between

 

 

30

two pieces of dry ice for 1 minute, then placed in the flask
attachment; 3) frozen immediately by immersion into an
alcohol-dry ice solution for 1 minute, then placed in the
flask. Following any of these treatments, the tissues were
immediately placed in the freeze-drying apparatus and dried
for a period of 5—8 hours. The tissues were then taken out
of the drying flask and immediately infiltrated with paraffin
in one of two ways: 1) infiltration for not less than 15
hours, in two paraffin baths in the autotechnicon; 2)
infiltrated under vacuum (15 1bs./sq. in.) for a period of
15, 30 or 60 minutes.

The tissues were then taken out of their respective
paraffin baths, and imbedded in paraffin. Blocks were cut,
mounted, sectioned and stained according to the usual procedure.

Frozen section technique.-—Tissues were taken from anes-
thetized and unanesthetized White Leghorn hens. The tissues
were sectioned on a Spencer—Freezing Microtome (Model 880)
in one of the following states: 1) fresh unfixed; 2) agar
imbedded (Lillie, 1954); 3) gelatin imbedded (Lillie, 1954);
or 4) fixated in 10 percent formalin. The sections were cut
at either 15-20 microns or 50-100 microns depending upon the
method employed. The sections were stained by the routine

procedure.

 

 

31

Celloidin technique.--Mature feathers are highly kera-
tinized, cylindrical structures which are devoid of any
material in their lumen. Due to these characteristics, it
is very difficult to section this type of tissue without
some shattering occurring. Thus, the section tends to
become distorted during histological processing. In an
attempt to eliminate some of the distorting effects, the
celloidin method of processing was used.

Tissues were taken from the leg and breast area of a
White Leghorn hen following death by bleeding. The bird
was then scalded for 1 1/2 minutes in water at a temperature
of 1400F. Following scalding, Zenker—formalin fixative was
injected, subcutaneous or intradermal, into the leg and
breast area. Tissues were taken at 1, 3, 5 or 11 minutes
after the fixative was injected. A11 tissues were processed
by the Hercules method for celloidin sections (Bensley and
Bensley, 1938). Sectioning the blocks of tissue was carried
out according to the cedarwood oil method for dry sections
of celloidin (Lillie, 1954). The sections were stained
using the method for staining celloidin sections (Armed

Forces Institute of Pathology. 1957).

 

RESULTS AND DISCUSSION

A. Anatomical studies.

General description.--The anatomical arrangement of the

 

feather follicles and the muscles which control their move-
ment is essentially as noted by Langley (1904), and is de-

scribed here to facilitate understanding of feather loosen—

 

ing. The feather follicles are arranged in rows and con-
nected to one another by bands of smooth muscles (Fig. 2).
Thus, when the dissected skin is viewed from the surface, a
four-sided figure is seen between any four follicles. In
the back region, the feather follicles are located further
apart anterior—posterior than laterally; consequently, the
typical figure usually observed is a rhomboid (Fig. 2).

The muscular system of the feather follicle is much more
complex than is indicated in Fig. 2. While it is true that
the muscles pass between the roots of adjoining feather
follicles, they do so in a unique pattern. After attaching
to the feather follicle by tendons, the muscle fibers course
from the dermal papilla area of one follicle to the apex
area of the follicle directly anterior to it. The muscle
fibers also course from the dermal papilla area of one folli—
cle to the apex area of the follicle directly posterior to it.

32

Fig.

2.

33

Photomicrograph of skin taken from the dorsal
feather tract of a turkey showing the general
view of the muscular arrangement between five
feather follicles. Prepared by dissection.

X 9.

A. Feather follicle

B. Muscle

 

35

Thus, it is quite obvious that in this manner the smooth
muscles form a criss-cross pattern. This pattern is very
adequately demonstrated in Fig. 3. In addition, muscle
fibers also course from the apex of one follicle to the
apex of an adjacent follicle. The purpose of these muscles
is to erect, depress or retract the feathers (Langley, 1904).
Fig. 4 is a photomicrograph of a dissected feather
follicle from the dorsal feather tract of a turkey. Similar
to the hair follicle, the feather follicle is dilated into
an onion—shaped area called the bulb. The bulb is the area
of the greatest diameter of the follicle. The feather
follicle is hollow at the base. This depression forms an
obovate cavity which is filled with loose connective tissue.
This, in turn, constitutes the area of the dermal papilla.
The resting feather follicle is surrounded at the base
by a loose capillary network which arises from larger blood
vessels at the base of the dermis. Evidence of blood vas—
cularity can be seen in the region of the neck of the folli—
cle. It is apparent from Fig. 4 that these blood vessels
arise from the same vessels that supply the base of the
follicle. During molt, the vascularity increases remarkably

and can be seen in abundance in follicles containing

36

mwaomSE mo mmOHUImeMU .O
OHUHHHOM Hwflpmwm .m ..<

.om N .COHpumm

QoNOHm .QOHDmHmmon ommnoumocflHOSO .mmaoflaaow Mofipmww
Dcwomhcm comBDmQ mmnsoo woSD mm mmaomSE mo QMoDumm mmono
Immfluo map mcflsonm coxoflnu m mo Down“ Hmsummw Hanson obs
Eonm Q®MMD cflxm mo coflpoom HMCHUSpflmQOH m mo smoumouoflfiouogm

 

.m

.mam

 

 

 

38

mHUflHHom uoflpmom mo wpfl>mo mcflnmbco Hommo> cooam -m

.mcoflpomnflc Hmum>om CH mcamusoo
can mao>oa wSOHHm> pm maoflaaom 0D coSUMme odomSE SDOOEm .Q

oHUHHHom nonpmom mo Qasm .O
>DH>MU opm>OQo mcflcflmpcoo maoflaaom Hoflpmom mo mmmm .m
maoflaaom Hmflpmom mo xomd .d

.om N .QOHpoommHU SQ coummonm .mmxnflu m mo uomnp Hmnumom
Hmmuoc map Eonw oaoflaaom Honpmom cmbommmflc m Mo fimwumouoHEODOLA

.a .63

 

 

 

4O

immature feathers (Fig. 5). As the developing feather
matures, the pulp, along with the blood vessels, is slowly
resorbed and is used to nourish the developing feather
(Lillie, 1940). At maturation, the pulp is completely
resorbed, hence the feather becomes a hollow keratinized
structure (Fig. 5).

According to Lillie (1940) the pulp is supplied with a
single axial artery which gives off many branches. The pulp
is replete with pericentral sinuses which connect to form
small veins. The veins, in turn, leave the follicle through
the papilla.

Numerous nerves may be seen emerging from the spinal
cord or from the spinal ganglia; however, as they course to
the skin they become microscopic and are virtually impossible
to trace macroscopically.

Histology.--In cross section, the lumen of a mature

 

feather appears as a clear white area which is devoid of any
structure (Fig. 6). In longitudinal sections of this area,
keratinized membranes marking the periodic steps in the
resorption of pulp can be seen. These membranes are the
scala of the calamus. In contrast, the cross-section of

the immature feather is characterized by the appearance of

4l

MHVCGETHG OHHUsUMHuaCOU .U

coapomm mmono .mHUmSE .m
COHpomm HmcflUSDHmCOH .oaomsz .m
mQHSQ Hmflpmom .Q

mammmm>

UOOHQ SDHB mpoamon mafia mcflcflmucoo .meUHHHom Hmfipmmm oHSumEEH .O..m
mHoHHHom Hofibmmm musumz .<

.om N .oSHQ mcflamcm m.cflmncmcflmm QDHB cocampm coauomm .copmnpmsHHH
omHm mum mucmfimam oHHDUMHDGOO .Um>Ho>QH mmHUmSE mflu mo wpflxmamaoo mflp
can mno£pmom mHSDmEEH mchHMDcoo moaofiaaom HmSDmmm 03p .Hmnpmom muspmfi

m mcflnflmpcou oHUHHHom Hmnpmmm m mQHBOSm Gogoflflo m mo uomnw Hmnpmmm
Hmmuoc map Scum cmMMD :flMm mo coauoom HmcHUSDHmQOH m mo smmumonoHEODOSQ

.mE

 

43

sesamauflmm
oHomSE fluooEm
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meww> cooam

waomsmnoo acaommlnoum>

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mammflp o>auowccou
ESHHoQUHmm

Edflaonuflgm ommflcflpmmwx
mSEmeo UoNHcHuman

Hmzpmom ocu mo coESq

.4

.OOH N .Eflmum

.mmcHUQSOHHSm mpfl cam maoflaaow

Hmflbwwm onsme m mo cofluumw mmono m mcHBOflm Qoxoflflo m mo Down» Hospmmm
Hmwnoc mflu Eonm coxmp cflxm mo Goapomm HmsflcsuflmcoH w mo ammnmouoflfiouonm

 

.o

.mflm

 

 

 

45

the pulp with its pericentral sinuses and axillary artery
together with the stratum corneun and ridges (Fig. 5).
Adjacent to the keratinized calamus of the feather proper,
is the keratinized layer of epithelium. In longitudinal
section, this layer can be readily traced as a continuation
of the epithelium of the skin (Fig. 7). The keratinized
layer of the feather proper and the keratinized layer of the
epithelium form a frictional bond which presumably aids in
holding the feather in its follicle. When the feather be-
comes loose in its follicle, these two layers separate and
form the follicular cavity (Fig. 8). Within the follicular
cavity, numerous microscopic bridges of adherence between
the two keratinized layers can be observed. When a feather
is plucked from its follicle, the keratinized layer of epi-
thelium remains attached to the follicular wall.

Lillie (1940) diagrammatically depicted the next layer
adjacent to the keratinized epithelium as a circular muscle
forming the follicular wall. Upon histological examination
of sections stained with a specific connective tissue stain
such as Masson's, Gomori's or Van Gieson s, it is very
apparent that this layer is not smooth muscle but, rather,

connective tissue. Moreover, the connective tissue layer

46

Hogumom mo mDEmamo cmwflcfiumnmx .U

oaoflaaom Hwflpmom mo ESHHoSDHmo chHcHumuwx .m

cflxm mo Edflaonuflmo coNHchwwa .<

.mm X .cflmoo can aflawxowmfiwmfl m_mHHHmm LDAB cmcHMDm coflpomm

.cflxm osu mo ESHHwSDHmw coNflcflpmuwx map SDAB msoscflpcoo mcHoQ mm oHUHHHow

Hoflbmww map mo Edflamflbflmm chHQHuman esp mcHBOSm coxoflfio m mo Downy
Hoflpmom HmmHOU map Eonm coxmw QHXm mo coapomm mmono m mo nmmumonoHEODonm

.mam

48

oaoflaaow Hoflpmom mo Esflamzuflmo pomflcflumnmx
mmpflnfl UflmoomOHUHE

>ufl>mo HMHSUHHHOM

Moaummw mo mSEMHMU cmNHcflumqu

Hmfipmom mfiu mo cmfidq

.<

.ooa x .cflmsosw coma m.omoaamw Suaz cmcHMDm coflpoom
.ESHHoSDflmo mo Howma cowacflumuox map can mSEmHmo conscaumnox map coozuob
moconmncm mo momcflun oaQoomonan map mQABOSm cmxoano m mo uomup nosumow
ammnoc esp Eoum coxmu cflxm mo coauoom HMQHUSDHmcoa m mo smmumouoHEODOEm

.m .mfim

 

 

50

is replete with elastic fibers. These elastic fibers form a
network around the feather and upon close examination can be
seen to be continuous with the tendon of the smooth muscle
(Fig. 9).

As a rule, the muscles are found in bundles; however, in
the skin they are often seen as singular muscle fibers scat-
tered among the connective tissue. When these smooth muscle
fibers parallel each other, they may unite to form a muscle
bundle. As the bundle approaches the feather follicle, it
abruptly ends in a tendon which is replete with elastic fibers.
This elastic tissue then combines with connective tissue to
form the follicular wall. These smooth muscles all arise
within the dermis and, as noted previously, can be seen cours-
ing from one follicle to another (Figs. 2, 3 and 5).

Numerous contraction bands were observed in the muscles
of the feather follicle (Fig. 5). These were the result of
smooth muscle cells being caught in a completely contracted
state by the fixative; thus, they appear shortened, bulged and
are stained more intensely than the rest of the muscle fibers.

Frequently seen in close association with the feather
follicle were the Vater-Pacini corpuscles (Figs. 6 and 10).

These corpuscles were numerous; usually one or two could be

Fig.

9.

51

Photomicrograph of a longitudinal section of skin
taken from the dorsal feather tract of a chicken
showing the attachment of smooth muscles to a
follicle containing an immature feather by tendons.
Section stained with Gomori's aldehyde fuchsin;
counterstained with metanil yellow. X 100.

A. Smooth muscle
B. Tendon containing elastic fibers
C. Continuation of elastic fibers in the

connective tissue of the follicular wall

    

'22: \

3‘953'5" "T‘

Fig.

10.

53

Photomicrograph of a longitudinal section of skin
taken from the dorsal feather tract of a chicken
showing the Vater-Pacini corpuscle in relation to
the feather follicle. Section stained with
Gomori's trichrome stain. X 35.

A. Vater-Pacini corpuscle
B. Connective tissue of follicular wall

C. Lumen of feather follicle

 

55

seen in relation to a given feather follicle. They were
observed in tissue taken from the back, leg, breast and neck
area. This corpuscle is an encapsulated nerve ending and is
composed of concentric/lamellae. In this study, their exact
location was not determined. However, Winkelmann and Myers
(1961) reported that they were located just above the inser-
tion of the multiple smooth muscle bundle on the feather
follicle.

The muscles of the feather follicle are richly supplied
with nerve fibers, as demonstrated by several stains used.
In Fig. 11 is shown a typical bundle of nerve fibers coursing
through the connective tissue stroma of the skin. From this

bundle of nerve fibers, numerous branches split off, one of
which is shown in Fig. 11. These branches can be traced for
some length before they penetrate the smooth muscles of the
feather follicle; however, due to the thickness of the sec-
tion required for nerve demonstration, this could not be
reproduced photographically. As the nerve fibers penetrated
the smooth muscles they were observed to do one of two things;
one, they continued to course through the muscle as a small
bundle; or, two, they branched repeatedly until individual

nerve fibers were formed (Fig. 12). These individual nerve

56

.QOHDUmm QmNOHm
ISUflmMQ cabana
mcflmusoo xasuu
map EOHM cmxmp

.OOH X

.UOfipoE Ho>HHm m.ccwEHoxcH3 .xcsnp came Eoum use
Hanan mpoz .mEOHDm mammflp m>flpooccoo map smsousu
o>HmQ m mQHBOSm GoXUafio m wo uomnp Hozpmmm Homnoc
cflxm mo coapoom Hmcflcsuflmcoa m mo gmmnmonoHEODOQm

.HH

.mflm

 

 

Hoflflm o>nmc HMSUH>HUGH .O

oHUQSQ o>noc HHmEm .m
mHUmDE bpooEm .4

8
5 .omv x

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oflp mcHBOSm cmXUHSU m mo Down“ Hmnummm menoc esp Eouw coxmu cflxm cfl
“commum mSmme HMHSUmSE mo QOHDUmm Hmcflcspfimcoa m mo SamumouoHEouozm

 

.NH

.83

 

 

 

6O

fibers apparently terminate in free nerve endings, as motor
end-plates could not be demonstrated. Although the nerves
were observed to be abundant in the connective tissue

stroma of the skin, as well as in the muscles of the feather
follicle, they were not observed in the follicular wall.

The muscles of the feather follicle were cholinesterase
reactive, thereby indicating the presence of cholinergic
nerves (Fig. 13). Both the acetyl and butyrylthiocholine
substrates were successful in the demonstration of choline—
sterase activity. When these substrates were eliminsted,
no staining reaction was observed. A nerve plexus as seen
surrounding the hair follicle by Montagna and Ellis (1957)
could not be shown around the feather follicle by the histo-
chemical method.

The remainder of the microscopic anatomy of the skin is
made up of the connective tissue stroma with an abundance

of adipose tissue and minute blood vessels (Fig. 6).

Other observations.——As previously stated, one of the
objectives of the histological study was to characterize the
essential changes involved in feather loosening. In an
attempt to secure this information, skin tissue was first
studied from birds which were scalded in water at a tempera-

ture of 1400 F for 1 1/2 minutes.

61

.00H x .QOHuommn ommuoummcHHOSUOHsuawpoofi
.Qoxoflno m mo Domup Hofipmmm Homnop may Eoum cmxmw QHXm cfl Dammoum
mHUmDE mo coauummn mmmnmumocflaosu Howamhp M MD LQMHmOMUHEODosm

.MH

.mfim

 

 

63

Observation of the scalded skin tissue in which the
feathers were removed immediately before processing, reveals
that much distortion of the tissue occurs during the process
of scalding (Fig. 14). This, in effect, made any detailed
histological analysis impossible, although it was observed
that the feather separated from its follicle at the kera-
tinized layer of epithelium. It is also evident from Fig.
14 that numerous contraction elements are present in the
muscle of the feather follicle. This finding is quite in-
teresting and suggests that muscle relaxation may not be
essential for feather loosening as the present theory indi-
cates. Sections of skin tissue taken from birds which were
scalded, but the feathers left intact, were also distorted
and incoherent.

In a further attempt to observe the histological changes
occurring in feather loosening, skin tissue from birds under
the influence of sodium pentobarbital was studied. Examina-
tion of skin tissues taken from birds in the anesthetized
state revealed no apparent differences from that taken from
unanesthetized birds. Thus, this suggested that skin from
the anesthetized bird underwent changes which allowed the

feathers to return to their tightened state before fixation

64

oaomsz .Q
mOHUHHHOm Hmflnwmwm .U.m.<

.mm X .GHMDm mm HnogmlcaamxoumEmL guHB cocamum

coapoom .mcflcamom mQHBOHHom cmxoflfio m mo Domuu Hocpmmm Hmmnoc
onp Eonm coMMD cflxm mo coapuow HmCHUDDHmcoH m mo SmmnmonoHEOUOSm

.wa

.mam

 

 

 

 

66

could occur. Consequently, a study was undertaken to deter-
mine if similar changes occurred in skin when it was removed
from an anesthetized bird.

Two White Leghorn hens were anesthetized with sodium
pentobarbital. Immediately thereafter, two sections of skin,
each approximately 2 X 2 inches, were taken from the back
region of each bird. Feather pulling force was then measured
on each of these tissues at the following times: immediately,
15, 30 and 60 minutes after the skin was removed from the
bird. For a control feather pulling force, data were obtained
before the birds were anesthetized.

Table 1. Feather pulling force of feathers pulled from
excised skin of anesthetized White Leghorn hens

 

 

Mean feather pulling force (gms)

 

 

Before Immed. 15 min. 30 min. 60 min.
after after after after
608 40 302 453 484

 

l"Before" feather pulling force obtained on birds before
anesthetization. All other values obtained from excised
skin.

As can be seen from the data presented in Table l, the
mean feather pulling force of feathers pulled from the skin

immediately after its removal from the body was markedly

67

decreased from the value obtained before the birds were
anesthetized. H0wever, this effect failed to persist.
Within 15 minutes after the skin was removed from the birds,
the feather pulling force returned to 50 percent of the
value obtained for the birds in the conscious state. As is
evident from the data, the feather pulling force continued
to increase from the value obtained immediately after the
skin was removed from the birds. At the 60 minute observa-
tion, the feather pulling returned to 80 percent of the
control value. Thus, it is obvious that changes were oc-
curring in the excised skin which allowed the feathers to
return to their tightened state.

Histological observations of molting feathers revealed
no information on the mechanism of feather release. The most
obvious difference between molting and mature feathers was
the presence of the pulp, together with the various layers
of the developing feather, in the follicle containing the
immature feather.

The previous study indicated that skin underwent some
change beginning immediately after it was removed from the
body. Thus, in a further attempt to observe the feather and

its immediate surroundings in the relaxed state, the freeze-

68

drying and frozen-section techniques were employed. In
addition, celloidin sections were studied.

Freeze—drying.-—Much difficulty was experienced in at—
tempting to produce microscopic sections of feather follicles
processed by this method. This was due to the brittleness
of the sheath of the feather proper. In addition, consider-
able difficulty was encountered with the process of paraffin
infiltration. Extended time periods of infiltration were
necessary when the autotechnicon paraffin baths were used.
However, even when the tissue was infiltrated up to 15 hours,
the infiltration still was far from being satisfactory.
Vacuum infiltration for 60 minutes was comparable to the
extended time period of infiltration in the autotechnicon.
Infiltration by vacuum for periods less than 60 minutes was
incomplete.

Frozen sections.-—Considerable difficulty was experienced

 

in sectioning unfixed, fresh skin tissue containing mature
feather follicles. Again the difficulty appeared to be due
to the brittleness of the feather sheath. Coherent sections
were virtually impossible. When the tissue was fixed in 10

percent formalin, the sections were markedly improved.

69

Due to the fixation time involved, the feather could not
be observed in the relaxed state. The gelatin and agar em—
bedding technique (Lillie, 1954) resulted in somewhat more
coherent sections. HOwever, when the medium was dissolved
for the purposes of staining, the sections failed to remain
intact.

Celloidin.-—The celloidin sections obtained did not
appear any more coherent than the paraffin sections routinely
processed. In addition, it was found that the celloidin
sections stained very intense, more so than is usually
desired. Due to these results, together with the lengthly

procedure involved, this method was only sparingly used.

70

B. Physiological Studies
EXPERIMENT I

Effect of piercing various parts of the brain on feather
pulling force.

No doubt there are many factors which may be involved
in relaxation of the muscles of the feather follicle and,
consequently, feather release. One such factor which is
known to influence feather release is the nervous system,
as indicated by feather loosening when a successful brain
stick is performed. What general part of the brain is in—
volved, however, is controversial. Therefore, it was the
purpose of this experiment to determine the general part of
the brain involved in the release of the feather from its
follicle.

A total of 25 birds were used in this study. The majority
of these birds were either White Leghorn or White Rock hens,
although some White Rock and White Leghorn cockerels were
used. After the normal feather pulling force was obtained,
each bird was hung by its feet from a shackle and the exter-
nal jugular vein severed. Immediately thereafter, the brain
was pierced with a sharp, narrow-bladed knife inserted

through the roof of the mouth. Following feather pulling

71

observations, the brain was dissected out of its cavity, and
gross studies of the course of the knife made. The course
of the knife was then plotted on a diagram of the brain for
later study. The immediate area of the brain through which
the knife passed was also processed for histological studies.
For the histological studies, the standard method of fixa-
tion, dehydration and infiltration was used. The sections
were stained with hematoxylin and eosin.

From 19 of the 25 birds studied, data on feather pulling
forces were obtained immediately after the stick was made.
The remaining 6 birds began struggling immediately after
their brains were pierced, thereby making it impossible to
obtain data until the struggling ceased. The individual data
are reported in Table 2.

A study of these data indicated that only two of the
13 birds in which the stick was made into the optic lobe or
cerebrum showed a significant reduction (P < 0.05) in feather
pulling force when measured within 2 minutes after the
stick was performed. In contrast, 11 of the 12 birds whose
brains were pierced in the area of the diencephalon, cerem
bellum and medulla showed a marked reduction in feather

pulling force. Neither the medulla nor the cerebellum were

72

pierced alone, consequently, it was impossible to accurately
pinpoint the part of the brain area involved. There is
some indication that the cerebellum may be the essential
part. This is evident from the fact that all birds in which
the stick was made in the area of the diencephalon—cerebellum
showed a marked reduction in feather pulling force. Birds
in which only the area of the diencephalon was pierced
showed only a small reduction in feather pulling force, thus
indicating that this general area has little influence on
feather loosening. Further evidence suggesting that the
cerebellum may be involved is found in the study of the bird
pierced in the optic lobe—cerebellum. It is obvious that
feather pulling force was markedly decreased in this bird.
On the other hand, birds pierced only in the optic lobe
showed little change in feather pulling force. When the
medulla and cerebellum were pierced simultaneously, feather
pulling force was markedly reduced, thus again suggesting
that the cerebellum may be involved.

The increase in feather pulling force between the two
observations following brain sticking was quite obvious.
This increase was greatest for those birds which showed the

greater reduction in feather pulling force and may be

73

attributed to the effects of struggling. Also attributed
to the effect of struggling was the large variation between
feather pulling forces of birds that were pierced in the
same general area.

Histologically, the course of the knife could be seen
very clearly. The most obvious indication that the knife
entered a given area was the infiltration of blood. It was
also noted that tissue separation occurred. Because the
knife generally entered more than one part of the brain, it
was again impossible for any conclusions to be made regard—

ing the essential part involved in feather release.

74

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mosaw> 03» may cmeuwQ ounom mcflaasm Honpmom CH mmcmgu ucoUHoQ map mucmwmnmmm .H

.xoaum muommn monom mundane “menace some “40.0 v me pgmummmae mauemoauaemam s.
.xoflpm whomwn monow mcHHHDm Hmflpmom EOHM Amo.o v mv pconMMHU mabcmoflmacmflm a

 

 

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I ¢.mml ssoa H mom I I mm H mmw Enaaoaonoo maascoz
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ssm.mma+ m.hHI mm H mmm o.HhI sec H maa mm H omm : :
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I m.H¢I ismm H mmm I I we H mom : :
ssm.hoa+ B.Hml asmm H mam n.0hl *iom H Hma ms H mew : ;
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ssm.m© + m.mm| *smm H mom m.oml seem H wmm mm H ems Esaaoflonou consmoocoHQ
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mecmnu mmcmso .QHE m omcmao Houmm Moflum Homuom Hmnpcmb
pcmouom pcoouom Hopwfi pawonom .cHE NIo mnowom

 

Amamv Hounm UHMUQMDm

munom mcflaasm Hmnbmmw cmmz

 

counmflmcflmun mo unmm

 

 

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mo oonom mcflaasm Monumwm no cflmun map mo mbnmm msoaum> mcaonoflm mo poommm .m magma

 

75

 

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mosam> OBD may CowBHoQ oouom mcHHHDQ Hosummm SH mmcmno pcmoumm on“ mucomonmom .H
.xoaum muoumn mouom meaafism umapmmm scum AHo.o v me pgmumumfle mapemuauaemflm ..
.MoHum whommn mouow mcHHHSQ HmQDmom Eoum Amo.o v mv meHoHHHU >apcmoHHHcmHm a

 

 

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pcmouom pamonmm Houmfi Hcmouom .QHE mIo onowmm

 

 

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mcHHHSQ HoSHon co GHMHQ map Ho muumm mDOHHm> mcHoanm mo uommmm .Ac.ucouv

 

 

.N OHQMB

76

EXPERIMENT II
Effect of neuromimetic, anesthetic and tranquilizing drugs
and drugs which depress the autonomic nervous system on
feather pulling force.

The objective of this experiment was to study the in-
fluence of the nervous system on feather release by using
four different classes of drugs, namely, anesthetics, tran-
quilizers, neuromimetics, and drugs which depress the auto-
nomic nervous system. In addition, it was thought that by
using drugs which act on the central nervous system, addi-
tional information could be obtained regarding the part of
the brain involved in feather release.

Sixty-seven White Leghorn hens and 15 White Rock broilers
were used in this experiment. Of these, 29 were given
neuromimetic drugs, 12 were administered tranquilizing drugs,
30 were given anesthetics, and the remaining 11 were given
blocking agents of the autonomic nervous system. The 15
White Rock broilers were used to study the effects of sodium
pentobarbital and constituted a portion of the group of 30
birds used to study the effects of anesthetics. A few of
the same birds were used in experiments involving different
neuromimetic drugs; however, a minimum time interval of at

least 5 days elapsed before any particular bird was re-used.

 

 

 

 

77

The neuromimetic drugs selected for use were: acetyl-
choline, pilocarpine and carbachol (parasympathomimetic);
epinephrine and ephedrine (sympathomimetic). Atropine (para-
sympatholytic) and yohimbine (sympatholytic) were the block-
ing agents studied. Several anesthetics were also used.
These included ethyl ether, chloroform, sodium pentobarbital
and procaine. Tranquilizers studied were chlorpromazine
(thorazine) and promazine (sparine). The pharmacology of
these drugs was described by Drill (1958). All drugs, with
the exception of promazine, ether and chloroform, were made
up in 0.85 percent physiological saline. Injections were
intravenous (i.v.), intramuscular (i.m.) or subcutaneous
(s.c.). The site of injection was: brachial vein for intra-
venous, thigh muscle for intramuscular and the loose skin
stretching medially between the thigh and the body for sub-
cutaneous, with the exception of procaine. This drug was
injected intradermally in the back region. Inhalation anes-
thetics (ether and chloroform) were administered by means of
a cone. With the exception of epinephrine, procaine, ether
and chloroform, all drugs were given on a per unit of body
weight basis. Only single injections were made. The amount

of the drug given may be seen in the respective tables.

78

Feather pulling forces were recorded before treatment,
immediately after treatment and at various intervals there—
after, depending upon the route of administration of the
drug involved. Various clinical symptoms were also observed
and were used as an indication of drug efficacy.

The results of the effects of various anesthetics on
feather pulling force are presented in Table 3. The data
showed a significant reduction (P < 0.01) in feather pulling
force for all drugs; however, ether appeared to be least
effective. Due to the peculiar arrangement of the bird's
respiratory system, the volatile anesthetics (ether and
chloroform) were difficult to administer. The duration of
anesthesia with either drug was short, consequently, the
reduction in feather pulling force was of brief duration.

In contrast, sodium pentobarbital was very effective in pro—
ducing anesthesia. Since the route of administration was
intravenous, anesthesia was produced immediately and the
feather pulling force was decreased by 77 percent of the
value found in the conscious bird. A similar effect was
observed when procaine, a local anesthetic, was administered.
This drug reduced feather pulling force by 80 percent in

the area immediately around the site of injection.

 

 

79

Reduced feather pulling force induced with the general
anesthetics was not surprising in view of the fact that the
center for feather loosening undoubtedly lies within some
portion of the central nervous system. The considerable
differences between the results obtained with ether and
chloroform are difficult to explain, especially since both

of these drugs are very similar in the mechanism of action

 

 

(Beckman, 1958). One possible explanation may be found in
the fact that chloroform as an anesthetic is much more potent
than ether. Thus, the birds which received chloroform may
have been anesthetized to a greater depth than those re-
ceiving ether. It was observed that birds anesthetized with
chloroform remained under anesthetization considerably
longer than birds anesthetized with ether.

The effects of the tranquilizing agents, chlorpromazine
and promazine, upon feather loosening are indicated in
Table 4. It is obvious that both drugs resulted in a marked
reduction in feather pulling force. The greatest reduction
in feather pulling force was noted immediately after injec-
tion of the higher level of promazine. On the other hand,
the greatest decrease caused by chlorpromazine did not occur

until the 10 minute observation. Moreover, the duration of

 

80

the effect of chlorpromazine appeared to be shorter than
that observed for promazine. Although no statistical anal-
ysis was applied to test the effectiveness of the differ-
ences in dosages, it is apparent that in both cases the
higher levels were more effective than the lower levels.

From the studies with procaine, it becomes evident that
the peripheral nervous system may also be involved in
feather release. The action of this drug is local. The
drug penetrates through the tissue down to the nerve end-
ings, paralyzing the function of the nerve. Nerve impulses
are, therefore, blocked from this area. As a result,
relaxation of the muscles of the feather follicle occurs
(feather loosening).

The results from experiments involving neuromimetic
drugs are summarized in Table 5. The data show that there
were no significant differences in feather pulling force as
a result of these drugs. Even with large doses, which
produced marked distress among most birds, feather pulling
force remained approximately the same as the value observed
in the normal state.

The data showing the effects of sympatholytic and para—

sympatholytic drugs on feather pulling force are shown in

 

81

Table 6. As is evident from the data presented, both atro-
pine and yohimbine significantly decreased (P < 0.01) the
feather pulling force from the value observed before drug
administration. Atropine was effective immediately, even
when injected intramuscularly. On the other hand, the sub-
cutaneous injection of yohimbine required approximately 30
minutes to produce its effect. Thus, these data suggest
that the muscles of the feather follicle are innervated by
both sympathetic and parasympathetic fibers and that either

or both may be involved in feather loosening.

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86

EXPERIMENT III
Effect of spinal transection on feather pulling force.

The results from the previous experiments indicated that
the nervous system was involved in the release of the feather
from its follicle. Moreover, it was apparent that a depres-
sion of the nervous system was essential in this phenomenon.
Since spinal transection may be regarded as suppressing the
nervous activity, it seems conceivable that feather loosen—
ing might occur upon severing of the spinal cord. Therefore,
the present experiment was undertaken to determine the
effect of spinal transection on feather release.

General.——Spina1 transections were performed in the
thoracic or lumbar—sacral region of birds which were lightly
anesthetized with sodium pentobarbital. Following anesthe—
tization, the muscles over the spinal column were separated
and the spinous process of the vertebra at the selected site
was clipped away. A bone drill was then used to reach the
cord. The cord was severed and picked out in small pieces
by a small forceps. The forceps were then directed caudally
and manipulated so as to disorganize the cord. The level
and completeness of the transection were confirmed by

autopsy.

87

Feather pulling forces were obtained by the routine pro—
cedure: however, in this experiment feathers were pulled
from three feather tracts, namely, dorsal, femoral and pec—
toral. With respect to the dorsal tract, data were obtained
from two different areas. One area was anterior to the
level of the spinal transection, the other, posterior to
the level of the spinal transection. The purpose of ob-
taining data anterior and posterior to the level of spinal
transection was two—fold. First, the anterior area could
serve as a control for the posterior area at any particular
time throughout the experiment. Secondly, the anterior
area could serve as a control against the effects of sodium
pentobarbital which is known to reduce the feather pulling
force.

Feathers were pulled before anesthetization and imme—
diately, 25 and 60 minutes following spinal transection.
Following the last feather pull, nine of the birds were
sacrificed in order to determine whether feather relaxation
observed in the live birds could be carried over into the
post-mortem state.

Thoracic spinal transection.-—Six White Leghorn hens

 

were used in this study. Two birds were subjected to spinal

88

transection at the level of the fourth thoracic vertebra
(T—4), one bird at the fifth thoracic vertebra (T—5), and
two birds at the sixth thoracic vertebra (T—6). In addition,
one other bird was subjected to a spinal transection at the
level of the third thoracic vertebra (T—3); however, feath-
ers from the pectoral tract were not pulled, thus there was
only a total of five birds studied with respect to this
feather tract.

The results from the effects of severing the spinal cord
in the thoracic region on feather pulling force may be seen
in Table 7. The data revealed that a significant reduction
in feather pulling force occurred in the dorsal feather
tract when the feathers were pulled posterior to the level
of the transection at each observation. In contrast, feath-
ers pulled anterior to the transection showed an increased
feather pulling force. This increase was significant
(P < 0.01) at the 25 minute observation and may be attributed,
in part, to the fact that it became necessary to pull feath—
ers anterior to the level at which they were pulled in the
normal state. This, of course, was necessitated when the
level of the transection was performed at the anterior part

of the back (thoracic vertebra). When values anterior and

89

posterior to the transection were compared, it was noted
that the feather pulling force posterior to the transection
was reduced by approximately the same value as it was re—
duced from the feather pulling force in the normal state.
Thus it is obvious that the effects observed are those
resulting from the spinal transection and not sodium pento—
barbital. This fact is further substantiated by the fact
that an increase in feather pulling force occurred anterior
to the level of spinal transection.

It can also be readily noted with respect to the femoral
feather tract that a 74 percent reduction (P < 0.01) occurred
in the force required to pull an individual feather from its
follicle immediately after the spinal transection was per—
formed. A similar effect was observable throughout the
experimental period.

The effect of thoracic transection on feather pulling
forces of feathers pulled from the pectoral tract is not as
clear as it is on the dorsal and femoral tract. As can be
seen from the data presented in Table 7, birds which were
subjected to spinal transection at the level of the fourth
or fifth thoracic vertebra showed a significant decrease in

feather pulling force whereas those sectioned at the level

90

of the sixth thoracic vertebra showed essentially no change.
The considerable differences in feather pulling force
between birds subjected to spinal transection at the level
of the fourth or fifth thoracic vertebra may be attributed
to the fact that nerves arising from the spinal cord branch
considerably as they course out to the periphery of the
body. As a result, they may innervate a large number of
muscles. Apparently, all of the feathers pulled from birds
subjected to spinal transections at the level of the fourth
thoracic vertebra were associated with muscles innervated
by nerves arising from the spinal cord posterior to the
level of transection. Thus, when the transection was per-
formed, these muscles lost their direct connection with the
brain. Consequently, the muscles relaxed and a reduction
in feather pulling force occurred. On the other hand,
feathers pulled from the pectoral tract of birds subjected
to spinal transections at the level of the fifth thoracic
vertebra have muscles innerved by nerves arising from the
spinal cord anterior to the level of the fifth thoracic
vertebra. Since these nerves branch considerably, it is
suggested that some of the feathers pulled from these birds

were associated with muscles which were in direct connection

91

with the brain, whereas other feathers may have been asso-
ciated with muscles in which this connection was severed.
Thus it may easily be seen that these results were subjected
to considerable variation, a fact that is indicative of the
large standard error which is reported. Although the num-
bers are small, these data suggest that the muscles of the
feather follicles in the pectoral tract may be innervated

by nerves arising from the spinal cord anterior to the level
of the sixth thoracic vertebra.

Lumbar—sacral spinal transection.-—Five White Leghorn
hens were used in this study. Spinal transections were
performed at the following levels: first (L-l), sixty (L—6),
eighth (L-8), twelfth (L-12), or thirteenth (L—l3) lumbar—
sacral vertebra. Feather pulling force was not obtained
from the pectoral feather tract of the bird subjected to
the transection at the level of the first lumbar-sacral
vertebra. Consequently, the results are reported as the
mean value for five birds on the dorsal feather tract and
four birds on the pectoral feather tract (Table 8). With
respect to the femoral feather tract, individual data are
presented (Table 9).

As can be seen from the data presented in Table 8, a

 

 

 

 

92

marked decrease in feather pulling force occurred only in

the dorsal feather tract, posterior to the level of the
spinal transection. Feather pulling force of feathers

pulled from the pectoral feather tract was significantly
decreased; however, it is obvious, as indicated by the per-
cent decrease, that this reduction was minor. Thus, these
data further support the earlier statement that in order

to loosen feathers in the pectoral feather tract, the cord
should be severed anterior to the level of the sixth thoracic
vertebra.

The results from the effect of severing the spinal cord
in the lumbar-sacral region on feather pulling force of
feathers pulled from the femoral tract may be seen in Table
9. A significant reduction in feather pulling force was
noted for each of the levels immediately after the spinal
transections were performed. Similar results were noted at
the 25~minute observation. At the 60—minute observation,
however, the results became complicated. It is obvious
that only the bird in which the spinal transection was per-
formed at the level of the first lumbar-sacral vertebra
continued to show a consistent decrease in feather pulling

force. The feather pulling force in all other birds, and

 

93

especially in the bird in which the transection was at the
thirteenth lumbar—sacral vertebra, increased considerably.
Although there appears to be a definite trend for the
feather pulling force at 60 minutes to increase above that
observed at 25 minutes, the values reported are still signi-
ficantly different (P < 0.01) from those observed in the
normal state with the exception of the bird in which the
cord was severed at the thirteenth lumbar-sacral vertebra.
Why this increase in feather pulling force occurred is dif—
ficult to explain. One explanation may be simply that
muscle tone, which undoubtedly is diminished following spinal
transection, may have been regained.

Carry—over effect.——Although the main objective of this

 

experiment was to contribute to the fundamental understand—
ing of how the nervous system may influence feather retention
and release, it was nevertheless important to obtain infor—
mation on the question: ”Can feather relaxation in the live
bird be carried over into the postemortem state?"

For this study nine White Leghorn hens which were sub—
jected to spinal transection tithe previous studies were
used. Two methods of killing were studied, namely, a lethal

dose of sodium pentobarbital and bleeding. In the case of

94

sodium pentobarbital, feathers were pulled from the dorsal
feather tract, both anterior and posterior to the spinal
transection, at the following times: before death, imme-
diately after death, and approximately 5 minutes after death.
On the other hand, for birds killed by bleeding, feathers
were pulled only posterior to the spinal transection before
death and after struggling.

It is obvious from the data presented in Table 10 that
with both methods of killing the feather pulling force
posterior to the transection increased very markedly after
death. In the case of sodium pentobarbital, this increase
was 94 percent of the value observed immediately before
drug administration, whereas in the case of bleeding this
increase was 160 percent. Thus, these data are in agreement

with those of Klose ep_gl. (1962).

 

95

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99

EX PE RIME NT IV
Effect of skeletal muscles on feather pulling force.

According to Langley (1904), the muscles which are respon—
sible for feather movement are of the involuntary type.
Furthermore, he indicated that only intra—dermal muscles
are involved. Since it is well known that the skin adheres
to a large proportion of the skeletal muscular system, it is
conceivable that muscles of the skeletal system could pos—
sibly influence feather release. This experiment was under—
taken to investigate the effect of skeletal muscle on feather
pulling force.

Curare, a drug which paralyzes skeletal muscle but not
smooth muscle, was used. The drug was injected intravenously
into each of eight White Leghorn hens. Five birds received
the drug at the dosage of 0.0267 mg/kg of body weight; the
remaining three birds were administered the drug at the
dosage of 0.05 mg/kg of body weight. Artificial respiration
was provided for birds administered the drug at the higher
level according to the method described by Burger and Lorenz
(1960). Data on feather pulling force were obtained on
feathers pulled from the dorsal feather tract in the usual

manner. Data were obtained before injection, immediately

100

after injection, and 5 minutes after the drug was adminis—

tered. The results of this study are presented in Table 11.

Table 11. Effect of a single intravenous injection of
curarel on feather pulling force of feathers
pulled from the dorsal feather tract of White
Leghorn hens

 

Mean feather pulling force i standard
error (gms)

 

 

 

No. Dosage Per Per
of (mg/ Before Immed. cent 5 min. cent
birds kg) ‘ admin. after change after change
+ + +
5 0.0267 622 — 55 602 — 57 —0.03 618 - 43 —0.0l
+ + +
3 0.05 584 — 12 567 — 28 —2.9 622 — 15 +6.5
1. Tubocurarine chloride.

From the data presented, it is apparent that curare had
very little effect on feather pulling force. No significant
differences were found between any of the observations when
tested against the value observed before drug administration.
Paralysis of the skeletal muscles of the leg was produced
immediately after the injection of the drug at both levels.
The higher level also paralyzed the respiratory muscles. At
the five minute observation, the degree of paralysis caused

by the lower level of the drug became variable to the extent

101

that three of the five birds were capable of body movement.
On the higher level all birds were still completely para-
lyzed at the five minute observation. Thus, it is suggested
that the skeletal muscles do not play a role in the release

of the feather from its follicle.

 

 

GENERAL DISCUSSION

A. Anatomical studies.

The findings obtained in this part of this investiga—
tion reveal that the feather follicles of domestic turkeys
and fowl are tubular structures, embedded into the dermis
layer of skin and connected to one another by a complex
system of involuntary muscles. The latter fact was not
surprising in View of the evidence presented by Langley
(1904) on the muscles which move the feathers. Further
confirmation of the observation by Langley (1904) was pro—
vided by the fact that these muscles were attached to the
feather follicle by elastic tendons. In the present study,
the elastic fibers were observed to continue in conjunc—
tion with connective tissue around the feather follicle,
thus forming the outermost layer of the follicular wall.
The fact that the outermost layer of the feather follicle
was found to be connective tissue is in disagreement with
Lillie (1940) who reported that the feather follicle was
enclosed by circular muscle. It should be pointed out,
however, that the detailed histological structure of this

tissue bears a marked similarity to that of smooth muscle.

102

103

In fact, when a general stain such as hematoxylin and eosin
Was used, it was virtually impossible to differentiate this
tissue from the smooth muscle of the feather follicle. Con-
sequently, unless a specific connective tissue stain is
used, it is quite probable that these two tissues could be
confused. As previously noted, when Masson"s connective
tissue stain was employed, there was a marked contrast in
the staining reaction between muscle and connective tissue.
This particular stain colors connective tissue blue and
muscle fibers red. In view of the fact that the layer in
question stained an intense blue, it was concluded that it
consisted of connective tissue. That this layer is connec-
tive tissue instead of smooth muscle was also noted by Lucas
(1962) and Stettenheim (1962).

The histological findings also clearly demonstrate that
the muscles of the feather follicle have a rich supply of
nerves. In view of the fact that these nerves are so closely
associated with the muscles of the feather follicles, they
undoubtedly consist of nerve fibers which are motor in
origin and which thereby function in feather movement. As
to whether these nerves also consist of fibers which are

sensory in origin is not known. It appears, however, that

 

 

 

104

they do since numerous sensory nerve endings (Vater-Pacini
corpuscles) were observed in close association with the
feather follicle. This view is substantiated by the fact
that nerve fibers of the Vater—Pacini corpuscles run chiefly
in the sensory fibers of mixed nerves supplying muscles,
tendons and blood vessels (Best and Taylor, 1961). Thus it
is conceivable that the nerves observed in the muscles of the
feather follicles are mixed nerves, i.e., consisting of both
motor and sensory fibers.

From the histological studies, it is difficult to deter—
mine whether these nerves represent the sympathetic or para—
sympathetic division of the autonomic nervous system. On
the evidence of Langley (1904), however, it seems more than
likely that at least the sympathetic system is present. This
would correspond with the innervation of the arrectores
pilorum of the mammalian hair follicle. Some evidence that
the parasympathetic system may be present stems from the
present histochemical studies. Although these studies were
somewhat limited, the presence of cholinesterase activity
was quite obvious. It is also quite possible that both
systems may be present. This is indicated by the physio—
logical studies of this investigation which will be discussed

later.

 

105

The fact that these nerves were not observed to terminate
in motor end-plates is consistent with the findings of Win—
kelmann (1960). Also in agreement with Winkelmann (1960)
was the observation of a network of nerve endings. Accord-
ing to Winkelmann (1960) this network is not a motor—end—
plate in the sense that they appear in striated muscles.

The demonstration of the_Vater-Pacini corpuscles was

 

not surprising in view of the fact that they were long known
to exist in the skin of birds (see Winkelmann and Myers, 1961
for review). These corpuscles, previously regarded as the
Herbst corpuscles, are anatomically similar to those of the
mammal. On the other hand, they display chemical properties
which separate them very distinctly from those of mammals
(Winkelmann, 1960). In the mammal these corpuscles are con-
sidered as pressure receptors, while in the bird there is
some controversy as to their function. They were formerly
thought to function as tactile receptors; however, recently
they have been considered to be vibration receptors (Marshall,
1961). In View of the fact that they are sensory end-organs
it is assumed that they do not function in the release of

the feather from its follicle. Although these corpuscles

were observed to be in close association with the feather

106

follicle in the present study, they are also known to be
present in the non—feathered skin, beak, tongue and genital
regions (Winkelmann and Myers, 1961).

Another histological observation which is worthy of
consideration is that of the follicular cavity. From the
semi—diagram presented by Lillie (1940) it can be seen that
this cavity exists between the sheath of the feather and
the epidermal lining of the follicular wall. In the present
study, this cavity was observed in many sections. On the
other hand, there were also many sections in which this
feature was not observed. It therefore becomes interesting
to raise the question as to whether this is a normal phenom-
enon or an artifact due to histological processing. The
author accepts the latter view since tiny strands of kera—
tinized epithelium (microscopic bridges) were seen to con—
nect the two epithelial layers when a cavity was present. It
is suggested that these microscopic bridges are formed as
the feather itself shrinks away from the keratinized layer
of epidermis.

A most interesting finding was that skin removed from
an anesthetized bird underwent changes which allowed feathers

to return to their tightened state. Just what the nature

107

of these changes were was not determined. The fact that
they occurred, in the absence of innervation, however,

strongly implies that the smooth muscles of the feather

follicles are involved. In particular, tonus may have been
regained. Physiologically, tonus may be of several ori—
gins: 1) it can be created by nerve impulses of low fre—

quency; 2) it can be brought about by asynchronous activity
in different parts of the muscle; or 3) it can originate
within the muscle fiber itself. When the skin is left
intact on an anesthetized bird, the degree of tonus is
undoubtedly depressed by the action of the anesthetic. When,
however, the tissue is removed from the bird, it becomes
conceivable that tonus may be regained through either the
second or third mechanism listed above. Consequently,
feathers become tight in their follicles.

Although lack of skin tissue containing feathers in the
loosened state makes it difficult to assess the histologi-
cal changes involved in feather loosening, it is neverthe-
less interesting to speculate on how some of the structures
observed might function in this phenomenon. As previously

stated, the present theory is based on the fact that heat

denatures proteins which are present in the muscle of the

108

feather follicle, thus allowing muscular relaxation and
feather loosening. In view of the large number of muscles
which were observed to be associated with the feather folli—
cle in this study, as well as their complexity, one must
agree with the above theory that the muscles are in some

way involved. Other constituents of the feather follicle,
however, should not be overlooked. Of particular impor-
tance are the elastic fibers which are located in the outer—
most layer of the follicular wall. These fibers undoubtedly
function in feather loosening and tightening, although the
exact way in which they function is not known. Since they
are continuous with the tendon connecting the muscle to the
follicle, it is suggested that they function synonymously
with the muscles of the feather follicle in the feather
release phenomenon.

As to whether or not the large number of nerves ob—
served in the muscles of the feather follicles are involved
in feather release remains obscure. It is well known, how-
ever, that the nervous system can in some way cause the
release of the feather from its follicle. If one makes the
assumption that these nerves are involved in feather release,

and in View of the physiological studies of this investigation

 

109

there is every reason to do so, one also must make the as—
sumption that they function in this phenomenon indirectly,
as in no case were nerves observed surrounding the feather
proper. It is suggested that the part played by the nervous
system in feather release is simply to stimulate or depress
the muscles of the feather follicle which, in turn, play

the active role in this phenomenon.

The actual site at which the feather separates from its
follicle appears to be at the keratinized layer of epithe—
lium. This is evidenced from the fact that when a feather
was plucked from its follicle, the keratinized layer of

epithelium remained attached to the follicular wall.

110

B. Physiological studies.

The significance of the results obtained in this portion
of the investigation is principally that of providing basic
information through which one might contemplate the physio—
logicallnechanisms involved in the release of the feather from
its follicle. In general, three observations provided in—
formation which demonstrated conclusively that the nervous
system was involved in this phenomenon: l) feathers loosened
when certain parts of the brain were pierced, but remained
tight when other areas were pierced; 2) various drugs which
function by acting on the nervous system resulted in feather
loosening; and 3) spinal transection resulted in feather
loosening posterior to the level of the transection.

In regard to the first of these observations, it is
apparent from the data (Table 2) that a center which influences
feather release may exist in the brain. Thus, this finding
is in agreement with the long recognized view that feather
loosening will occur if the proper part of the brain is
pierced (King, 1920; Weaver, 1936; Klose gt al,, 1962). The
general part of the brain which is involved in feather
release could not be determined from the data obtained in

Experiment I, simply because of the fact that usually more

111

than one part was involved in the stick. The data (Table 2)
would seem to indicate, however, that the cerebellum or
medulla is the essential part.

In this connection, it is of interest to reiterate the
fact that both the medulla and the cerebellum were reported
to contain a center for feather loosening. As previously
mentioned, King (1920) reported that the medulla was the
essential part, whereas weaver (1936) was of the opinion that
the center was located in the cerebellum. In view of the
results obtained in Experiment II with general anesthetics,
the reports of both King and Weaver became somewhat ques—
tionable. It will be recalled that both of these workers
studied the part of the brain involved in feather loosening
in birds which are under the influence of anesthesia. In
the case of King, ether was used, whereas Weaver employed
chloroform. Since in the present experiment both of these
drugs reduced feather pulling force from the value observed
in the conscious state, it raises the question as to whether
the feathers on birds which the above two workers were
studying were loosened by the anesthetic or by the destruc—
tion of certain brain tissue. It is of interest to note
that King (1920) reported that ether had no effect on the

muscles of the feather follicle.

112

Although the data (Table 2) seem to indicate that the
general part of the brain involved in feather release is
the medulla or the cerebellum, the possibility that the di-
encephalon may be the essential part should not be over—
looked. Evidence to support this contention is contained
in the data obtained from the effect of tranquilizing drugs
on feather pulling force (Table 4). The fact that chlor-
promazine and promazine reduced feather pulling force was
not completely surprising since other tranquilizing agents
were previously shown to produce this same effect (Sturkie
_£._l., 1958; Klose _t_al., 1961, 1962; Knapp and Newell,
1961). The exact manner in which these tranquilizing agents
cause feather loosening is not known. One explanation may
be the fact that the peripheral effect of chlorpromazine
and promazine are due to a depression of sympathetic nervous
activity (Beckman, 1958). This View is substantiated by
the present finding that the sympatholytic agent, yohimbine,
decreased feather pulling force (Table 6). Whether chlor-
promazine and promazine depress sympathetic nervous activity
centrally or peripherally is not known. It is known, how—

ever, that the tranquilizing agent, reserpine, decreases

sympathetic outflow at the hypothalamic level of the

 

 

113

diencephalon (Beckman, 1958; Drill, 1958). Thus, in View
of this fact, it is possible that tranquilizing agents may
cause feather loosening by depression of the sympathetic
center in the hypothalamic area of the diencephalon. It is
conceivable therefore, that during brain—sticking the sym—
pathetic center in the hypothalamic area of the diencephalon
may be damaged which, in turn, results in feather loosening.
It is interesting to note that during brain—sticking via

the roof of the mouth the knife generally passes through
this area.

Although the above explanation attributed feather loosen—
ing to a decrease in sympathetic nervous activity, it is also
apparent from the data presented in Table 6 that suppression
of the parasympathetic nervous system will result in a
reduced feather pulling force. Hence, this finding is in
agreement with those of King (1920) who reported atropine
and scopolamine to cause feather loosening. Feather loosen—
ing induced with atropine may be attributed to a paralysis
of the parasympathetic nerve fibers in the muscles of the
feather follicle.

The finding that either yohimbine or atropine resulted

in feather loosening suggests that the muscles of the

114

feather follicles are innervated by sympathetic and para—
sympathetic fibers of the autonomic nervous system. More—
over, it is apparent that these nerves must be depressed in
order for feather loosening to occur, a fact which was also
indicated by the data obtained from studies with anesthetics
and tranquilizers.

Further evidence that suppression of the nervous system
is necessary for feather release is contained in the spinal
transection study. It is obvious from the data obtained on
the spinal transected birds, that when motor impulses from
a higher brain center were interrupted by severing the spinal
cord, feather loosening occurred posterior to the level of
the transection.

It may be argued, however, that feather loosening ob—
served in spinal transected birds may have been due to spinal
shock. It is well known that when the spinal cord is severed,
spinal shock occurs. Although no experiment was carried out
to study the effects of spinal shock, it was assumed by the
author to have an insignificant effect on feather pulling
force. The basis of this assumption was two~fold. First,
spinal shock may be regarded as a general phenomenon, i.e.,

it affects the entire body. Thus, if spinal shock affects

115

feather pulling force, it should do so over the entire body.
Since feather pulling force anterior to the level of tran—
section remained approximately the same, as opposed to a
marked decrease posterior to the transection, it is taken
as evidence that the results observed were not influenced
by spinal shock. The second basis for this assumption
originates from the following data that were obtained from

a bird which was kept four days after the spinal cord was

 

 

 

severed.

Table 12. Effect of spinal transection at the thoracic
level on feather pulling force of feathers pulled
from the dorsal feather tract of a White Leghorn
hen

Relationship Mean feather pulling force (gms)

to spinal

transection Before 1 hour 2 days 4 days

Anterior 724 868 860 829

Posterior 844 172 218 294

 

It is obvious from these data that feather pulling force
posterior to the transection was markedly reduced from that
observed anterior to the transection, thus again suggesting
that spinal shock had very little, if any, effect on feather

pulling force.

116

The fact that reduced feather pulling force observed in
the live bird could not be carried over into the early post—
mortem state when the bird was sacrificed by bleeding is a
most interesting finding. No doubt this was due to the
effects of struggling. Klose et a1. (1962) also reported
that feather pulling force increased very rapidly following
death by bleeding. It cannot be stated, however, that
struggling is the only factor involved in causing feather
pulling force to increase after death. It was shown in

t al. (1962) that if

this study and previously by Klose
struggling was minimized by virtue of anesthesia, feather
pulling force also increased following death, although at a
much slower rate. This again suggests that some change
occurs in the skin which allows the feathers to return to

their tightened state.

SUMMARY AND C ONCLUSI ONS

The first part of this investigation was undertaken to
characterize the anatomical features of the feather follicle
and its immediate surroundings in the tightened and loosened
state. Both gross and histological studies were conducted.
The macroscopic anatomy was studied in skin taken from the
dorsal feather tract of a ”cooked”I turkey, whereas the micro-
scopic studies were of tissues generally taken from the
dorsal feather tract of chickens. From these anatomical
studies the following conclusions were drawn:

1. The feather follicle is a tubular structure and is em—
bedded well into the dermis layer of skin.

2. The feather follicle is supplied with a complex system
of smooth muscles which arise within the dermis. These
muscles attach to the feather follicle by tendons which,
in turn, are replete with elastic fibers.

3. The outermost layer of the follicular wall is composed
of collagen connective tissues.

4. A rich supply of nerves was demonstrated in the connec—
tive tissue stroma of the skin and muscles of the feather

follicles. The nerves apparently terminate in free nerve

117

 

118

endings. Histochemically, cholinergic nerves were

shown to be present.

Numerous Vater—Pacini corpuscles were present in the
feather area of the skin. They were observed to be in
close association with the feather follicle.

Numerous contraction bands were observed in the muscles
surrounding the feather follicle. They were observed

in tissue taken from birds in the anesthetized, unanes-
thetized and scalded state.

No appreciable histological differences were observed
between feather follicles present in skin taken from
birds in the anesthetized and unanesthetized state. This
undoubtedly was due to the fact that the feather follicle
returned to its normal physiological state before complete
fixation occurred.

Sections of skin from birds which were subjected to
scalding were too distorted for any detailed histological
analysis to be made.

The technique of freeze—drying was not satisfactory for
the study of the feather follicle in this investigation.
Frozen sections of un—fixed tissue were also unsatisfac—

tory for any detailed histological studies to be made.

119

The second portion of this investigation concerned a

series of experiments in which various physiological phenom—

ena were evaluated for their effect upon the release of the

feather from its follicle. Feather pulling force, as

measured by a spring scale, was used as the criterion. The

following conclusions were drawn from these physiological

studies:

1.

The exact part of the brain that is involved in the
release of the feather from its follicle was not com—
pletely determined. The data indicate that the dien-
cephalon, medulla or cerebellum may be the essential
part.

All of the general anesthetics, sodium pentobarbital,
chloroform and ether, significantly decreased feather
pulling force from the value obtained in the conscious
state. The local anesthetic, procaine, also had a sig—
nificant effect on decreasing feather pulling force
immediately around the site of injection.

Tranquilizing drugs, chlorpromazine and promazine, sig—
nificantly reduced the force required to pull an indi-

vidual feather from its follicle.

120

Atropine and yohimbine, blocking agents of the parasym—
pathetic and sympathetic system respectively, signifi—
cantly decreased the force required for feather removal.
None of the neuromimetic drugs used, however, signifi—
cantly altered feather pulling force.

All levels of spinal cord transections significantly
reduced feather pulling force of feathers pulled from
the dorsal feather tract posterior to the level of the
transection. In contrast, feather pulling force of
feathers pulled anterior to the spinal transection re—
mained relatively unchanged.

Feathers pulled from the femoral feather tract showed a
significant reduction in pulling force immediately and
25 minutes after the spinal cord was severed regardless
of the level of transection. However, only spinal tran—
sections anterior to the second lumbar vertebra had a
consistent effect on reducing feather pulling force at
the 60 minute observation.

Spinal transections at the level of the sixth thoracic
vertebra and posterior to this level, failed to have a
loosening effect on the feathers of the pectoral feather

tract.

121

Skeletal muscles do not influence the release of the
feather from its follicle.

Reduced feather pulling forces increased rapidly to
near their normal value following death of birds by
bleeding. When birds were sacrificed by a lethal dose
of sodium pentobarbital, feather pulling forces also
returned to near their normal value. The return, how—
ever, was much slower than that observed for birds

sacrificed by bleeding.

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Bensley, R. R. and S. H. Bensley, 1938. Handbook 9: Histo—
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