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THE MICROSCOPE ANATOMY OF THE

SMALL INTESTINES OF DOMESTIC ANIMALS

Thesis {at Hm Degree 51‘ M. S.

MICHIGAN STATE CS'LLEGE

Charles W Tii'kmnayer
“1951

 

 

 
  
 
 
  
 
  
 
 
 
  
  
   

This is to certify that the

thesis entitled

The microscopic anatomr of the small
intestines of domestic animals

presented by

Charles W. Titkemeyer

has been accepted towards fulfillment
of the requirements for

ms. degree mm

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Major professor

Date August 10, 1951

 

 

 

      

      

    

       

      

     
      

 

    

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TIE MICROSCOPIC ANATOMY OF
THE SMAIL INTESTINES OF
DOWSTIC ANIMALS

By
Charla s W. ”'lfitkemeyer

A Thesis
Submitted to the School of Graduate Studies of
Michigan State College of Agriculture and
Applied Science in partial fulfillment
of the requirements for the degree
of

MASTER OF SCIENCE

Department of Anatomy
1951

ACKNOWLEDGMENTS

The author wishes to express his sincere appreciation
to Dr. M. Lois Calhoun under whose supervision this project
was conducted. Her unfailing interest and constant en-
couragement were an inspiration and a challenge. Thanks
are extended also to Miss Esther Smith and Mr. William
Youatt for their assistance in photography.

Grateful acknowledgment is due to Mr. Robert Kader
for technical assistance; to Dr. Frederick Smithcors and
Dr. Frank Thorpe, Jr. for helpful assistance; and to
Mrs. Titkemeyer for proof-reading and typing.

A vote of thanks is expressed to all the scientists
and workers of the past who perfected the materials and
methods used on this project.

TABLE OF CONTENTS

INTRODUCTION

REVIEW 01r LITERATURE

General Plan of the Gastro-Intestinal Tract
The Small Intestine
Length and Capacity of Small Intestine
Macroscopic Features
Microscopic Features
Factors Affecting the Appearance of the

. Intestinal Mucosa

MATERIALS AND METHODS

RESULTS AND DISCUSSION
MacroscOpic Features
MicroscOpic Findings

SUMMARY AND 0 ON CLUSI CNS

LITERATURE CITED

33
33
35
59

63

INTRODUCTION

Scientific literature is filled with descriptions of
the digestive tract of man.> Anatomists, histologists,
pathologists and cytologists have written.much concerning-the
structure of this very important segment of man's body.
Strangely enough, very little has been.written about the
intestinal tracts of domestic animals. It is true that many
authors have.mentioned certain peculiarities in animal
digestive tracts but few have made an actua1.comparative.
study. Ellenberger (1911) and Trautman and Fiebiger (1931)
have published excellent German texts concerning.microscopic
anatomy of animals, but there is no English translation.

Most histological research workers have been content
with describing only certain features of the digestive tract.
In this category is Hans Elias (19h?) who has written the
article "Comparison of Duodenal Glands in Domestic Animals."
Others have satisfied themselves with a gross description of
the tract and have done little more than give comparative
lengths and capacities of the various segments.

This paper is an attempt at correlating the data already
written on the subject and at giving a description of a study
made on the microscopic anatomy of the small intestines of
certain domestic animals. .For this problem the horse, cow,
sheep, pig, dog, goat, and cat were the species studied.

REVIEW OF LITERATURE

No textbook on.microscopic anatomy is complete without
a section on the intestinal tract. However, the majority of
such books describe only the intestinal tract of the human
species. A.good histology text for veterinary students in
English is difficult to find. Those of maximow and Bloom.(l9h8)
Bailey (l9h8) or Ham (1950) are used by most veterinary
colleges. These books are all well written but are primarily
discussions of human anatomy. Therefore, in spite of the
abundance of material on the digestive tract, not much has
been written comparing the digestive tracts of domestic

animals.

General Plan of the Castro-Intestinal Tract

The digestive apparatus consists of the organs directly
concerned in the reception and digestion of food, its passage
through the body, and the expulsion of the unabsorbed portion.
The components of the digestive tube of animals include
the oral cavity, pharynx, esophagus, stomach, small intestine,
large intestine, and the rectum. Ruminants differ somewhat
in.that the stomach is divided into four compartments.

The general structure of the digestive tube follows a
definite pattern. From the lumen of the canal outward, there

are.mucous, submucous,.muscu1ar and serous coats. In the

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stomach and intestines, this plan is followed throughout.

In the esophagus the serous coat is replaced with a fibrous
one, and in the pharynx the submucous coat is absent and a
fibrous coat replaces the serous. In the mouth this definite
pattern is not followed at all, although the mucous membrane
is intact and continuous with the.mucous covering of the
contiguous parts of the canal.

Except for a difference in nomenclature Williams (1926),
Davidson (1937), Sisson and Grosamant(l938), Bailey (19h8),
laximow and Bloom (l9h8). Nonidez and Windle.(19h9). Francis
and Knowlton (1950), and.Ham.(l950) are agreed on the

anatomical concepts outlined above.

The Small Intestine

The small intestine is subdivided into three segments.
The first portion, attached to the pylorus of the stomach,
occupies a fixed position and is termed the duodenum. It
received its name, according to MWFadyean (188h) because in
man its length was about equal to the breadth of 12 fingers.
The remainder of the small intestine has a comparatively
loose.mode of suspension. It is arbitrarily divided into
Jejunum.and ileum, the former succeeding the duodenum and
the latter comprising the remainder of the tube. These terms
'were also borrowed from human anatomy where the term Jejunum
was applied because that portion of the intestine was generally
found empty in the dead body, while the ileum.was so desig-

nated because of its convoluted disposition. The small

- a-
intestine, as its name implies, is of smaller caliber than
the large intestine. moreover, it is distinguished from
nearly every part of the large intestine by having a smooth

and regular contour when distended.

Length and Capacity of Small Intestine

Kingsley (1926) found that the length of the intestine
was roughly related to the food, being longer in the plant-
eating than in the carnivorous species. This was strikingly
shown in frogs, where the tadpole (larva) had a very long
intestine correlated with the vegetable food, while the
adult flesh-eating frog had a tract hardly longer than that
of a tadpole of half the size.

Among the domesticated animals, ruminants have the
longest intestinal tract. Paton and Orr (1920) found that
the small intestine of the ox had an.average length of about
130 feet and a diameter of about two inches. This was
corroborated by Sisson.and Grossman.(l938). The latter workers
stated that the duodenum occupied three or four feet of this
length. The same authors found that the small intestine of
the sheep was about eighty feet long; its average diameter
was about an inch, the caliber increasing in its terminal part.

The horse has the next longest intestinal tract. Sisson
and Grossman (1938) observed that the average length was about
seventy feet and when distended, its diameter varied from

three to four inches. Its capacity was about 12 gallons.

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The duodenum was about three to four feet long. The average
diameter of the jejuno-ileum was about two and. one-half to
three inches. The last three or four feet were usually
tightly contracted resembling somewhat the terminal part of
the 'esOphagus. This part was termed the ileum. M'Fadyean
(1881.) gave the length of the small intestine of the horse
as 72feet. This was in very close agreement with measure-
ments of Fllenberger (l9ll).

Sisson and Grossman (1938) found that the small intestine
of the pig was about 50 to 85 feet in length. The first two
feet were firmly attached by mesentery and were termed duo-
denum. .

Jordan (191.0) found the small intestine of man to be
21; feet long. He broke down the three segments as follows:
duodenum, about 11 inches; the jejunum, about nine feet; and
the ileum about ll feet. The duodenum lacked a mesentery;
it was only partially enve10ped by a serosa, and it had the
greatest diameter, about two inches. Below the duodenum the
caliber of the small intestine gradually decreased until the
diameter was a little over an inch at the end of the ileum.
Cunningham (1931) agreed that the length of the duodenum was
11 inches. 'He stated that the diameter varied considerably
and averaged about one and one-half inches when empty but was
two inches or more in diameter when distended. '

The intestines of the carnivores are remarkable for

their. shortness and small volume. Chauveau (1872) stated

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that in a dog of ordinary size. the entire intestinal tract
measured scarcely more than lifeet of which 2‘. W28 inches
were for the large intestine. The capacity of the small-
intestine was given as one quart. Sisson and Grossman (1938)
gave the average length in the dog as 13 feet. Vever (191.8)
found the length to be six times that of the length of the
body.

The cat had an even shorter tract. Chauveau (1872) gave
the lengthas six feet: and the capacity as one-fourth pint.
Reighard and Jennings (1923) gave the lengthof the duodenum
as five inches. summys (1888) found. that the length of .
the duodenum of the cat was It to 16 centimeters. This
figure was in agreementwith. that given ..by Reighard and
Jennings (1923). Vever (19%) found that the ratio of body
length to intestinal length of the cat was four to one.

lacrosccpi 8. Features

Plicae circulares. The surface area. of the small in-
testine is greatly. increasedthrough the formation of
circular folds. These folds are called valves of Kirkring,
plicae circulares, or valvulae conniventes. They are con-
stant structures and do not disappear even when. the intes-
tinal wall is distended. when and Bloom (191.8) .found in
man that they began at a distance of 2 to 5 on- from the
pylorus and reached their maximal development in the distal
half of the duodenum and the proximal part of the jejunum.

.7-
In the ileum they became smaller and «less numerous and ,
disappeared in its riddle. In the .lower duodenum, they
reached a height of 8 mm. and usually extended over two-thirds
of the circumference. These folds were formed by all the
layers of the mucosa including the muscularis mucosa; their
core was subnucosa.

Lambert (191.8) found that the plicae circulares were
low and broadwhere they first appeared near the middle
portion of the duodenum and became taller and narrower toward
its lower end. Inthe JeJunum, they reached their greatest
development where they were tall, thin structures with .
secondary and tertiary folds which-gave them. the appearance
of being branched. They became lowerand less complicated
in the ileum where they seldom showed secondary or tertiary
folds. ‘

Williams (1926) stated that the valvulae conniventes
began about two inches beyond the pylorus at which. place the
mucous coat showed numerous transverse folds that ran about
halfway around the inside of the tube. They became fewer
and lower as they approached .the cecum,so that in the lower
ileum they occurred only as. isolated sickle-shaped folds-
These were similar to those found in the stomach, but differed
in the permanence of their form. When the stomach was dis-
tended the rugae disappeared; the valvulae conniventes were
pernanent structures. This. was confirmed by the observation
of newer (19157 ). She found that the whole moons coat and

.3.
muscularis mucosae were thrown up into folds, the valvulae
conniventes, which did not disappear when the wall was
stretched.

Joust (19h?) stated that the plicae circulares were
absent in‘athe horse and dog but. were presentinthe ox._
Sisson and Grossman (1938.) confirmed that. there were per--
nanent transverse. folds of the mucousmembrane (plicae
circulares) in the ox. These investigators made no mention,
of this structure in. their. descriptionof. the intestinal
tracts of the horse. pig, and dog. I .

Pezer's mtcheg. Other. macroscopic features. are the
Peyer's patches- According to Dorland..(l951) they are.
aggregations of. lymphatic ..,u..u. w -feund...chiefly . in . the . ileum.
Oowdry (19%) found that these masses of noduleswere. within
the tunica propria'and {were usually on the side of. the
intestine opposite the. mesentery. Bailey. (19“) in his
description of Peyer's patches. inhumananatomy described
them as being aggregations. of solitary follicles or groups
of lymph nodulesfound mainly in the ileum especially near
its junction with the jejunum. He found. that, they always.
occurred on the side of the gut opposite the attachment. of
the mesentery. Each patch consisted, of. from ten to. seventy
nodules,which lay side. by. side and (weresc arranged that
the entire patch had a generally. oval . shape, its long diameter
lying lengthwise of the intestine.

.9-

Bailey (191.8) also found that the pear-shaped apices of
the follicle were. directed toward the lumen and projected
almost through the mucosa. They were not covered by villi;

a single layer of columnar epithelium alone separated them
from the lumen of the gut, where their smooth. surfaces could
readily be seen in gross dissection. . The bases of the nodules
were not confined to. the lamina propria but extended into the
submucosa. The relation of the patch to the mucosaand sub-
mucosa could be appreciated best by following the course of
the muscularis mucosae. This was seen .to itOp abruptly at
the circumference of the patch. It appeared throughout the
patch as isolated groups of smooth muscle cells. Sometimes
the individual nodules which make up a .Peyer's patch were
quite discrete and well defined. More frequently, however,
the nodules tended to coalesceexcept at .their. spices, so
that the individual nodules could be outlined definitely
only at their spices and to some extent be identified by
their germinal centers-

In the horse, Sisson and Grossman (.1938) observed that
the patches were situated chieflyalong thesurface opposite
the mesenteric attachment andbegan about, three or four feet
from the pylorus. According to Illenberger (1911.) they .
numbered one to two hundred, andwereusually. one or two
inches long and one-quarter to one-half inch wide. Larger
ones occurred in the terminal . part, where one patch had a
length of seven to fifteen inches and a width of one-half

-10-
to one inch. They varied much in number, sine, and distri-
bution in different individuals and. underwent atrophy in old
subjects. These observations confirmed thework of Strange-
ways (1888) in which he found that the Peyer's patches in

the horse were oval or circular groups of solitarynodules
located in the jejunum and. ileum, and were most numerous

near the termination of the ileum.

In the ox, Sisson and Grossman (1938) reported that the
Peyer's patches were larger and more prominent and distinct
than in the horse. They varied greatly in size and number.
In adult cattle there were 18 to 1.0; in calves 20 to 58. They
usually formed narrow bands. There was a patch close to the
ileo-cecal valve.

Chauveau (1872) found that the Peyer's patches were less
numerous in the ox than in solipeds. but were larger in size.
A rather extensive Peyer's patch was found near the terminal
portion of the small intestine of the sheep. Chauveau (1872)
found that in both the sheep and the goat, they were often
more than eight inches in length and extended to the ileo-
cecal valve.

In the pig the patches were numerous, very distinct,
and band-like. Sisson and Grossman (1938) counted from 16
to 38. They found that they began eight to twenty inches
from the pylorus and extended intermittently to the cecum.
Ohauveau (1872) found an immense "Peyerian gland" in the

Q

. . -11- . .
latter portion of the small intestine, a band measuring from
five to six and one-half feet in length.

The dog had about twenty Peyer's patches according to
Sisson and Grossman (1938) and Chauveau (1872). Chauyeau
found five or six in the cat. Ellenberger (1911) found that
they were usually elliptical in outline but the last one was
band-like, reached to the end of the ileum, and was four to

sixteen inches long in young dogs.

macroscopic Features..

Villi--size,_shape and number. One of the outstanding
features of the.microscoPic anatomy of the intestinal tract
is the presence of villi thickly distributed over the entire
mucous surface of the small intestine. Their purpose is
absorption. The villi are small, finger-like processes
consisting of vascular loops, chyle vessels, fine muscular
fibers, and a covering of columnar epithelium. Since they
are projections of.mucous.membrane, they have cores of
lamina propria. The.muscularis mucosae and the submucosa
do not extend into them.as they do in the plicae circulares.
They are barely visible to the unaided eye and impart a
characteristic velvety appearance to the inner surface of
the small intestine.

In the duodenum, Piersol (1910) observed that they
appeared close to the pylorus,.but were better developed

farther distally, where they were low and broad and measured

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0.2 to 0.5 mm. in height and 0.3 to 1.0 mm. in widthin man.
He further observed .that.in the jejunum. the villi were conical
and somewhatlaterally compressed, while in the. ileum, their
shape was cylindrical, filiform or wedge-like and their
height was from 0.5 to 1.0 mm. ,

Gunningham (1931) also investigated the villi of the
human intestine and obtained approximately thesame results.
He found that beginning at the .edge. of the pyloric valve,
the villi were broad but short in theduodenum, and grew
narrower distally to the valvulae. c011,. at ..the edge of
which they ceased. They were found not only on the general
surface of the mucous membrane,.. but also. upon the plicae
circulares. Whilethey werenot present over thesolitary
lymph nodules, they were found in the intervals between the.
individual nodes of the aggregated nodules- This work was
corroborated by Lewis and. Bremer (.1930).

V Hill (193k) determined that villi'were the mostnumerous
in the upper part of the. intestine wherethey numbered.

fifty to eighty to the square inch. They were larger but
more slender and. less numerous in the ileum where they
numbered forty to sixty to the. linear inch. Their total
number in the small intestine. was estimated at four million.

Kendall (191.7) found that the shapes of the villi
varied from leaf-like through finger-likewto broadly club-
shaped. Bramer and Weatherford (19“.) stated that in the
duodenum the villi were low, leaf-like folds 0.2 to 0.5 mm.

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in height while those in the jejunum and ileum were rounded,
finger-like projections from 0.2 to 1.0 mm. .in height. They
also maintained that their shape could not be determined
from inspecting single sections. Lambert (191.8) found that
villi were broad and leaf-like in the duodenum, club-shaped
but smaller and fewer in numberein the ileum.

One of the few references made to the villi of mammals
other than man was made by Jordan (191.0). He stated that
they varied much in form in different mammals and in
different portions of the canal in the same individual.

He found that they were the most highly develOped in the
dog, where they formed long projections with expanded or
clubbed extremities and a constricted base or neck.

Hartman and Straus (1933) in describing the villi of
the monkey stated that in the duodenum they had the form
of small flanges and were dispersed in a transverse axis
to the tube. Those in the distal portion, the lower ileum,
were true villi appearing as pile on a plush fabric. In
the mid-region there was found a mixture of both types.
roust (19h?) found that the villi were long and slender in
the carnivores, short and plump in ruminants, and inter-
mediate in horses and swine. . Calhoun (1933) found that the
villi of the chicken were branched.

The villi, as Humbleton (1911.) and King and Arnold (1922)

pointed out are capable of various movements. Wells and

 

Ili.lllll..l [11" I II II]

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Johnson (l93h) described three types of movements: (1) the
tonic retraction associated with contraction of the mus-
cularis mucosae. (2) the swaying.movaments of individual
villi without shortening, and (3) the rhythmic retractions
in.which the villi shorten as much as half of their.total
length. The epithelium is able to adapt itself to these
changes by the adjusting of the individual cells and by the
folding of the epithelial coat. The cells appear to be
able to undergo considerable amounts of compression.and
stretching without injury.» .

The covering epithelium. :Host workers regarded the
entire epithelial complex.as.originating from entodermt
.irey (l9h6) stated that villi.begin to appear in the human
embryo at eight weeks after fertilization as.independent
rounded elevations of epithelium. The intestinal epithelium
forms an.unbroken layer of cells lining the small and large
intestine and composes the smaller glands and ducts which
empty into these tubes.

1 The columnar absorbing cells are by far the.most
numerous, characteristic and important elements of the
villus epithelium. :Kahn.(l9h6) found.that each villus was
covered with about three thousand of.these.cells.. Their .
form.is variable. The individual differences.result.from
pressure or tension from adjoining cells, fluctuations in

functional state and position on the villus.

.15-

Cowdry (1932) found that .the height of these cells ranged
from 20 to 26 microns, and varied with the degree .of extension
or contraction. of the villus, the cells inthe shortened
villus being longer and thinner. The width of the free end
of the cell averaged about nine microns, while that of the
base was quite variable and averagedsix microns or less.

lost histologists are agreed that these cells have
striated, cuticular free borders. Smithcors (1916) stated
that the striated. cuticular border affords protection from
abrasion of food particles and attack by digestive enzymes,
and that the borders of adjacent cells are joined by the
cuticle thus preventingpenetration between. the cells.

Goblet cells. Gowdry (1932) found that goblet cells
were quite numerous in the small intestine but not as
abundant as in the large intestine. According to him they
arose from a primitive form of cell, elaborated. mucigen in
a process similar. to that of other acinous -cell. glands,
and discharged this material directly into the crypt or.
lumen of the intestine. Real and Band (.1926) found that
the secretion of these glands stimulated. peristalsis and
lubricated the surface of.the. intestine. .

crypts of Lieberkiihn- Crypts of Lieberkiihn are simple
tubular glands of the mucous membrane itself. in (1950)
found that the cells in the deepest part of the crypts
secrete many enzymes. He stated that they secrete a com-
plement of proteolytic ones, particularly erepsin, which

.15-
act in the later stages of protein digestion .to produce
amino acids. Other enzymes secreted are those that convert
disaccharides into monosaccharides and special enzymes which
act upon the nucleic acid of nucleoproteins-

Martin and Banks. (191.0) observed that 166 grams of the
mucous membrane of a dog's small intestine. produced 1900 to
2,000 cc. of glandular. secretion every.21e hours. Volborth
(1925) proved that the mucous membrane of.the duodenum
and jejunum secreted the succusentericus which contained
in addition to secretin at least seven .differentenzymes.

Piersol (1910) reported that the crypts of Lieberkiihn
were very closely set and penetrated the tunica propria
as far as the muscularis mucosae. In length, he found that
they varied from 0.2 to 0.1. mm., and in diameter from 60
to 80 microns.

Johnson (1913) found that in strongly distended in-
testines bothvilli. and crypts became muchless. conspicuous
and in some cases were obliterated- He also found that the
crypts of the large intestine were considerably longer than
those of the small and reached a length of 0.7 mm. in the
rectum.

Among the cell types covering the crypts are the
columnar absorbing. cells and goblet cells similar to those
on the villi, and the cells of Paneth. Cowdry (1932) found
that these cells of Paneth. were characterized by their very

conspicuous granules. He cited the work of numerous German

.17-

workers who had found these cells in various species. Among
those cited by him were Holler (1899) who failed to find them
in the pig, cat and dog, Trautman (1910) who found them

in the latter two, Martin (1910) andHanmerI (1923) who
reported them in the large intestine of domestic animals and Ka-
wamura (1930) who found them totally absent in the duo-
denum of the rabbit but two to five per section present in
the rest of the small intestine. Ham (1950) found that.
these cells were probably responsible for producing most of
the enzymes formed in the intestine itself.

Other cells in the crypts of Lieberkfihn are the
argentaffine (enterochromaffine) cells. Ham (1950) found
that they were dispersed in a solitary fashion between the
other cells of the region. Their shapes varied in relation
to their position. 0n the villi, they were columnar, but
in the crypts they tended to be triangular. In the crypts,
moreover, their spices tended to be withdrawn slightly
from the surface and. their bases crowded between the bases
of adjacent cells and the basement membrane. He suggested
that these cells were concerned in the production of the
anti-anemic factor (of Castle). . .

The muscularismucosae. The muscularis mucosaeis the
third and outermost layer of the mucous membrane. Ham (1950)
found that it consisted of two thin layers of smooth muscle
fibers t0gether with varying amounts of elastic tissue and

.13-
that the fibers of the inner layer were circularly disposed,
the outer, longitudinally. Kingand Robinson. (191.5) found
that the museularis mucosae was well developed. in the gastro-
intestinal tract of all mammals and birds,-a1though its»
thickness was not the same for all species. Maximow and
Bloom (191.8) statedthat its thickness in the human intestine
was 38 microns. King 3; _a_l_. (19h?) found that the muscu-
laris mucosae of the dog's small intestine contained- both
longitudinal and, circular layers of. muscle at all levels.

;l_r__unn0r's M. Brunner'sglands are of the branched
tubule-alveolar type. They appear in the. region of the
sphincter of the pylorus with the first glands of Lieber-
kiihn. Sometimes they extend into the pyloric region for
several centimeters. The glands. erelocated for the most
part in the submucosa. while .the ducts pierce the museularis
mucosae. The cells are of the mucous type, .cuboidal
glandular cells. containing fine granules- In the distal
two-thirds, the glands gradually diminish in size and
finally disappear. In some cases they extend well into the
upper part of the jejunum. ,.

Elias (191.7) made a comprehensive comparison of, the
duodenal glands of..domestic animals. .and found. that in the
hog the Brunner's glands. formed. large continuous. masses
which filled the entire submucosa of the- proximal duodenum.
They were interrupted only by groups of fat cells. These

.19..
glandular masses appeared very much like oral, mucous
salivary glands. They consisted of very long and very
much twisted tubules. The lumina of the tubules were very
narrow, Just as narrow as those of the acini of the oral
salivary glands. As in those, the nuclei of the glandular
cells were slightly flattened, deeply staining, and located
at the basal periphery of the cells. The ducts were lined
by the same kind of cells which were found in the tubules.

In the horse, the duodenal glands formed small, distinct
lobules consisting of twisted tubules, essentially shorter
than those of the hog (Elias 191.7). Each lobule was .
provided with a duct. The end pieces were. similar to those
of the hog. The luminawere extremely narrow .and. the cells
which lined them were pyramidal to ouboidal. Their nuclei
were definitely flattened and pressed toward. the basal
boundaries of the cells where. they. caused a slight out-
bulging. The lumina. of. the ducts were wide and their lining
was a layer of low cuboidal cells.

Brunner's glands in the cat also formed lobules. but
they were less distinct than those in the horse (Elias 191.7).
The end pieces were tubulo-alveolar; branching occurred in
peripheral districts. The lumina of the end pieces were
small, but easily distinguishable. The glandular cells were
much smaller thnn in the horse. . Their nuclei werespherical,
and they did not stain as heavily as thoseof. the .pig and

the horse. Frequently, a large nucleolus could be

-20-
distinguished. 0n the whole, the nuclei resembled those of
pancreatic cells. The lumina of the ducts were as large

as those of the largest alveoli. The ducts were lined by

the same kind of cells that lined the and pieces.

Elias (19h?) found that, except for larger lumina,
the glands of Brunner in the ox were similar to those of the
cat. The glandular cells were small and cuboidal, and were
provided.with.relatively large,.light, spherical nuclei.
A.remarkable feature of the bovine duodenal glands was that
the end pieces which were directed upward, i.e., those
which approached the museularis.mucosae from.below, were
serous in character. The glands emptied frequently into
the crypts of Lieberkfihn.

In the dog, Elias (191.7) found that the glands of Brunner
had relatively large lumina and resembled flattened pouches.
They were lined by most characteristic, very tall, columnar
cells which were provided with distinct striated distal
borders. The nuclei were found near the periphery of the
glands. They were either flattened, slightly compressed,
or tall and oval. The ducts were lined by the same type of
cells that was found in the and pieces.

The ovine glands of Brunner had still larger lumina.
Their general shape was somewhat intermediate between the
branched, alveolar type of the ox and the flattened pouch
type of the dog. The glandular cells were columnar, but
not as tall as those of the dog. The distal border of the

-21..
cells was at some places provided with thin protoplasmic
projections deeply staining at their bases. The nuclei were
light staining.

According to Elias (191.7) the largest lumina among
the glands of Brunner. in domestic animals were possessed. by
the goat. Brunner's glands in this species consisted of
large, thin-walled, branched alveoli which very much re-
sembled hypoactive thyroid follicles. .The alveoli were. lined
by low columnar to low cuboidal epithelium. The. epithelium
of some alveoli was. provided with a deeply staining border.
The nuclei varied in shape from flattened to erect oval. A
few of the end pieces, however, were narrow tubules.

Elias (191+?) .ooncluded thatnthere was a great difference
in the size of the .lumina in the glandsof Brunner ranging
fran approximately two microns in the pig to one hundred
microns in the goat with the horse, cat, ox, dog and sheep
falling between the two in that order- .He also found that.
the lowest cells were five micronsin height and ,the tallest
were thirty microns in the following succession (low to high):
cat, ox, horse, pig, sheep, and dog. Joust (191.3). Winters
and funk (191.6) and Calhoun (1933) found that there were no
Brenner's glandsin the chicken. .

Dukes (191.3) made a fistula about .5 cm. long in the
duodenum of a. goat and obtainedJ. cc. of intestinal Juice
per hour indicating a secretion of nearly 100 cc. daily from

-22-
the small portion of the intestine containing duodenal glands.
He found that the duodenal-gland-containing part of the
intestine was the only part which gave an. abundant secretion.
Florey and Harding (1931.) made an extensive study of the.
secretion of the duodenal. glands .in the goat, pig, dog, cat,
and rabbit. They theorized that the. function of the duo-
denal glands was toprotect the mucosa from stomach acid
injury. This protection was effected by the alkaline se-
cretion of these. glands-

mscle layer. The muscular coat consists of two well-i
formed layers of smooth muscle separated .by a thin layer. of
fibrous connective tissue. The. inner layer, is circular,
the outer one is longitudinal. . In theaconnective tissue
between thetwo layers is the prominentmyenteric. plexus-
Along the. histologists .in agreement .with. these facts are.
lhrshall and Lazier (19w). Maximow and Bloom.(l9l.8),

Bailey (191.8). Romer (191.9). and Ban (1950)..

Cunningham (1931) found that in the small intestines of
many mamals the layers were not truly circular or longi-
tudinal, but were both spiral, the inner ecat- forming a
close spiral and the outer, a long spiral.“ Inthe inner
coat he found one complete turn madein every 0..5.to 1.0 mm.
or less while those of theouter .coat. made a. complete. turn
in every 200 to 500 m. or more. Arey and Elsen (1950)
disputed this claim. They conducted experiments on the small
intestines of the cat, dog, hog, and human by pulling free

.. . _‘23f .
relatively narrow ribbands of muscle and allowing these
stripped bands to follow their natural courses of separation
from the main muscle layer. The divergence fromstraight
directions were then measured and their trends determined.
The results showed that the longitudinal layer of muscle was
truly longitudinal with respect to the mesentery and the
circular layer was likewise truly circular. Neither layer
spiraled significantly.

Physiologists are agreed that the circular layer con-
striots the tube and the longitudinal ., one shortensit. The
combined action of constriction and shortening gives rise to
a movement known as the peristaltic .wavewhich results in
forcing the food ahead of the constricted segments.

Vever (191.8) stated that. compared to .the intestines of
other animls, those of carnivores have thicker and stronger
walls. This enables the animal. to deal with the large
pieces ‘of relatively indigestible flesh and bone which
form its diet.

m. L11 histologists are agreed that the small in-
testine is covered by a thin layer of. fibrous connective
tissue upon which rests a layer of. mesothelium. This
visceral peritoneum is reflected onto the mesentery along
the line of attachment to the intestine. Most of the human
duodenum lacks a mesentery and has only a partial serous

coat.

-24-

ractors Affecting the.dppearance of the Intestinal mucosa
Effects of distention of the intestine. Johnson (1913)
cited the'work of Heitzmann (l868) who discovered that the
shapes of villi varied with the distention of the intestine.
Heitzmann found that a piece of intestine of a freshly
killed guinea-pig possessed alternating contracted and.dis-
tended portions, and that if the piece were thrown into a
chronic acid.mixture, the contracted portions remained
permanently contracted and the distended portions perma-
nently distended. Ens examination of the villi.of the
contracted portion showed them.to be long and cylindrical;
of the distended portion, flat and conical. moreover, he
observed that artificial distention, produced.by.filling
a tied-off piece of intestine with.chromic acid mixture.
beyond the limdts of ordinary normal expansion, or extreme
distention caused by the formation of gas in the intestine,
almost entirely obliterated the villi. This he found was
true not only for the villi of the guinea-pig, but tola
less extent for those of the rabbit and cat. He.concluded,
therefore, that there was.no fixed form for the villi, but
that their shapes were dependent.upon.the.contraction.of
the intestinal tube. ‘He believed that during the.movements.
of normal peristalsis there was a continual changing in the
form.of the villi. He also noted that the intrinsic muscle
fibers of the villi acted as the antagonists of those of
the museularis of the intestinal wall.

-25-

In a study of intestinal contraction, Mall (1896)
found that the injection of oil into tied-off pieces of
intestine of the dog broughtabout a shortening of both
villi and glands and that up to a certain limit, the shorten-
ing varied directly with the amount of distention.

Harvey (1908) studied the large intestines of. the dog
and man and found that the length and breadth of the
intestinal glands varied with distention and contraction
ofthe intestinal tube. From a limited number of observations
he concluded that the glands of the transverse colon were
subject normally to greater changes in. length and breadth,
and those of the ascending colon to. smaller changes, than
the glands of other parts of the large. intestine. He made
no mention of the effects of distention upon the villi and
glands of the smallintestine...

The work of Bujard (1909) cited by Johnson (1913)
indicated the following results: In herbivorous mls,
where a large residuum of food materialwas found in the
intestine, the intestine was long .and the villi. small. and
few. In insectivores, frugivores, and omnivores, wherethere
was only a moderateamount offoodmaterial present,.the
length of the intestine was medium. and the villi large and
numerous. In the carnivores, where. a minimum residuum of
food was left, the intestine was shorterand the villi were

narrow, long and pointed, and very numerous. However,

-25-
Bujard (1909) made no.mention of the fact that it was the
amount of residuum.which.determined the amount of distention
of the intestine, and that it was this in turn which deter-
mined the shape of the villi. He believed, rather, that it
was the nature of the food material itself which.was the
active factor in producing different shapes- To substantiate
this view he performed experiments on the intestines of
white rats, in which he found that after the continued
feeding (lhO to 380 days) of milk and meat diets, the villi
became long and narrow, while on vegetarian diets, the
villi became broader and shorter. Unfortunately, in his
descriptions of villi, he did not state whether the pieces
of intestine he examined were in the contracted, partially
contracted, or in a distended state.

Johnson (1913) made an extensive study of the effects
of distention of the intestine. He made numerous.measure-
.ments showing the effects of the distention of the small
intestine upon the shape of the villi and glands when the
intestine was normally contracted, normally distended and
experimentally distended. For his work he used such animals
as the rat, guinea-pig, cat and the dog. He enumerated
the effects of distention of the intestines as follows:

(1) The outer intestinal coats became reduced in thickness.
(2) The.muoosa became reduced in thickness. (3) The
villi became shorter and broader. (h) Glands became

shorter and broader. In the guinea-pig and mouse they

-27-
entirely disappeared if the intestine was strongly distended.
(5) In the intestine of the guinea-pig. the epithelium became
flattened upon strong distention.

Johnson (1913) further stated that it was evident from
the foregoing results that the shapesof villi and glands
were to a great extent dependent upon the condition of dis-
tention or contraction of the. intestine. This was true
not only for marked distention produced experimentally, but
for the smaller amounts of distention which took place under
normal conditions. It seemed probable, therefore, that
with each dilation and contraction ofnormal peristalsis
and of the rhythmical movements of the intestine, the villi
changed their shape, and in. this way broughtabout a more
thorough mixing of the intestinal contents. Because of the
variety of shapes presented by the gland cavities. it was
not possible by ordinary methods todetermine their exact
capacities, but it was probable that the capacities of the
glands were decreased upon strong... distention, and. their
contents were then partially emptied into the lumen of the
intestines.

Effects of agonal and pest-marten chages. Guyer. (191.3)
found that the intestinal tract was one of the first tissues
to be affected by post-marten changes. He stated that
inasmuch as the intestinal. lining began. to digest itself.
promptly, tissues. from the. alimentary. tractshould. be the
first to be removed and placed in the fixing fluid. In a

 

_ -28-

personal discussion of this problem, Dr. Hans Elias (1951)
stated that he was convinced that the lining epithelium of
the intestinal tract was affected by digestive processes
within a very few moments following death. It was his
Opinion that any detailed study of the epithelium of the
intestinal tract should be done with tissues taken from
animals embalmed immediately upon the onset of death.

Sohn.and Arey (1951) found that.certain cells of the.
intestinal tract did not deteriorate rapidly. They main-
tained that, contrary to the usual Opinion that argentaffine
cells are extremely.labile, it can be shown that they per-
sist in the intestine for an astonishing length of time.
In a demonstration of this.phenomsnon.at the Sixtybfourth
Annual Session of the American Association of Anatomists,.
these workers showed that the argentaffine cells remained
normal for about 2k hours after death. .Between.h8 and 96
hours there was deterioration until not more than.one-ha1f
of all the argentaffine cells still appeared essentially
normal. Between 9c and 168 hours there.was further deteri-
oration and, although perhaps one-third were then_undemonp
strable, the.remainder still stained.even though they were
.more or less atypical. .The persistence was better in the
duodenum.of the dog than in the rabbit; in the.sigmoid-rectum
region, the reverse was true. In view of the prompt degenera-
tion of the mucosa as a whole, the long continued persistence

of recognizable argentaffine cells was remarkable.

-29-

Macklin and thklin (1926) found that the epithelium
of the villi underwent agonal and post-mortem changes very
rapidly. A.few minutes after the cessation of the circu-
lation in the intestinal wall, the epithelial cap of the
villus usually separated from.the underlying core, and soon
disintegrated. Frequently the core was pulled out of the
cap like a finger from.a glove. Sections of these detached
collapsed caps, such as are often seen in autopsy material,
looked like irregular and frequently broken epithelial rings.
This curious ”ballooning" of the cap seemed to be due to the
asphyxially induced contraction of the smooth muscle of
the villus core, with squeezing of the tissue fluid from.
the core underneath the epithelial layer, which became
broken away as a consequence.

Effects of inanition. The appearance.of the epithelium
depends to a large extent upon the state of nutrition of.the
animal. Bats which had been underfed for varying periods
revealed to Miller (1927) that the villi and glands were
atrOphic or degenerated completely. Sun (1926) found that
the length of time necessary to bring about this alteration
with malnutrition was much less in winter than in summer,
one day of starvation in the winter.months being sufficient
to reduce the epithelium.of the intestine of the mouse to
a mass of debris. With rereading,.the appearance became

normal if the starvation had not been too prolonged.

_ -30-

Miscellaneous effects. Parasitism affects the mucosa
of the intestinal tract principally through irritation and
hemorrhage. It sometimes causes a diarrhea which affects
the epithelial lining of the tract.

X-radiation is another factor which has a pronounced
effect upon the mucosa. Warren and Whipple (1922) found
that histological changes could be noted on the first day
after exposure, even before the appearance of clinical mani-
festations. The cells showed definite nuclear changes.
Degeneration of the crypt epithelium was evident before any
alterations were visible in the villus cells. This finding
is in the reverse of that in autolysis of normal intestines
after death.

From the above discussion of factors affecting the normal
histology of the digestive tract it is evident that any true
picture of this segment can be obtained only by careful
selection of the animals to be studiedand by the. elimina-
tion of as many variables as possible. The effects of
distention are the only cnesthat are difficult to eliminate.
Much of the variation in results obtained by different
workers can probably be attributed to this cause.

MATERIALS. AND METHODS

For this study the intestinal tracts from 39 animals
were used. Included in this group were twelve dogs, seven
cows, seven horses, seven pigs, two sheep, two cats, and
two goats. The intestinal tracts were fixed as soon after
death as possible. The intestines of the cows and pigs were
obtained from a slaughter house where it was impractical to
remove them immediatelyupon the death of the animal. They
were, however, fixed upon their removal from the carcasses,
usually within one-half hour after death. The intestinal
tracts of the dogs, cats, and horses were fixed within a
very few moments after death. Those of the sheep and goats
were obtained from specimens embalmed upon death and were
in good condition.

A gross examination of the tract was made before fixa-
tion to determine gross appearance of the villi and the
number of Peyer's patches. Sections were then taken from
the tract every'tenth distance irrespective of the over-all
length. The first section was taken as near the pylorus
of the stomach as possible and the last one was taken next
to the ileo-cecal, junction. The other eight sections were
taken equidistant between them. These sections were then
fixed either in Bouin's solution or in F. A. A. (Lavdowsky's)

-32-

mixture (Guyer 19h3). .After proper fixation, they were
dehydrated in dioxane, embedded in paraffin and sectioned
at 8 microns thickness. .

Two different staining techniques were used. Hematoxylin
and eosin (Guyer 19L3) were used on one set of slides to
facilitate the study of the villi and the glands. weigert's
and‘van Giescn's stains (Guyer l9h3) were used on another '
set as an aid for studying the connective tissue and muscle

layers.

RESULTS AND DISCUSSION

Macroscopic Features

211;. The gross examination of the intestinal tracts
revealed that the villi of the cat were much longer than
those of the other species studied. 11111 of the dog were
next in length, followed in order by those of the goat,
sheep, pig, horse, and cow. No attempt was. madcat measur-
ing the villi macroscopically. Plate I shows .a merosoopic
view of the villi in the duodenum of.a dog.

geler'sjatches. The presence of Peyer's patches varied
considerably in the various species. In the ”cat, none were
found grossly, but they were found microscopically. In the
horse, the first patch was found only about four feet from
the pylorus indicating that. Peyer's patches were located
throughout the jejunum and ileum. '.As the duodenum of the
horse extended for the first» three to four feet according
to the findings. of Sisson. and Grossman (1938.), Peyer's
patches began just subsequent to the terminal end of (the
duodenum. From this point on they were scattered inter-
mittently throughout the rest of the tract. They were
always on the side opposite the mesentery and varied greatly
in size and number. In the horses studied they ranged from
one-half inch to eight inches in length and numbered

-34-
approximately 85 per animal. This is somewhat less than
the one hundred to two hundred found by Ellenberger (1911).
Sane of the smaller ones probably were overlooked.

In the cow, Peyer's patches were much larger and more
prominent than they were in (the horse, but they were less
numerous. Upon gross examination an average of 18 per
animal was found. These ranged from two to twelve inches
in length and were scattered throughout the jejunum and
ileum. The sheep and goats had a few scattered Peyer's
patches throughout the jejunum and ileum. In one sheep
a Peyer' s patch was found extending from the ileum for
a short distance into the cecum.

The pigs had about twenty Peyer's patches each. They
were prominent and easily distinguishable. The large ter-
minal patch mentioned by Chauveau (1872) was not seen.

In the dog, Payer's patches were easily counted from
the exterior surface. (They appeared as circumscribed
elevations about three-fourths inch long and one-half inch
wide. As a rule they were not directly opposite the
mesentery but appeared on either side of it. The number
of patches ranged from 17 to 26 with an average number of
22. They were more. numerous in (the anterior part of the
mall intestine than in the ileum. Several patches were
found in the duodenum partially covered by the pancreas.

-35-
They formed a distinct elevation on the interior surface
of the tract. Plates II and III showmacroscopic views of
typical Peyer's patches in the. pig and dog.

Plicae circulares. Plicae circulares were found only
in the ruminants. The horse, dog, cat and pig had no cir-
cular folds although they did have longitudinal ones
running intermittently throughout the intestinal tract.

The longitudinal folds of the horse were very prominent

but did not assumes circular direction at any level. This
is in accordance with the views of. Foust (191.7) that plicae
circulares are absent in the horse and dog but are. present

in the ox.

Microscopic Findings

A microscopic survey of histological sections prepared
from various levels of the intestinal .tracts revealed num-
erous variations. Measurements included. the height of.the
villi, the height of the epithelium of thevilli, the
thickness of the museularis mucosae, the width of the lumen
of the Brunner's glands, the height of the epithelium of
Brunner's glands and the thickness of the muscle layers.
A review of the. results follows.

Height of the villi. Piersol (1910), Robinson (1931),
and mu (1931.) found in the human that theheight of the
villi tended to increase progressively toward the terminal

.35..
end of the small intestine. This phenomenon was not con-
firmed in the tracts of domestic animals in this investiga-
tion. There was no significant difference in the lengths
of the villi in the three segments of the tract. This
held true for all animals studied.

The greatest height was founlin the intestine of the
cat (Plate IV) where the villi had an average height of
963 microns. They were very close tOgether, quite slender
and somewhat constricted at their bases. There was some -
branching. They were also.more numerous.than in the other
species. The epithelial cells covering the villi were lower
in the cat than in any of the other animals studied and
reached a height of only 16 microns-

In the dog (Plate V), the height of the villi was next
in magnitude and reached an average height of 6L5 microns.
The villi were numerous and showed some branching. The
distal ends were expanded and club-shaped. The height of
the covering epithelium was greater than in any other species
and reached a height of 32.microns.

The goat had the next tallest villi. They averaged 615
microns in height and were wider at the base than those of
the carnivores. They were somewhat expanded at both ends

with a slight constriction in between. The epithelial layer
reached a height of 28 microns.

-37-

The villi of the sheep (Plate VI) and swine (Plate VII)
were next in length.and were nearly equal. Sheep averages
totaled L83.microns while those of.the hogs totaled h70.microns.
In both cases the villi were cylindrical and were arranged
in rows. Those of the swine were less numerous than in the
other species studied. The height of the epithelial.cower-
ing was 25 microns in sheep and 29 microns in swine.

The horse (Plate VIII) had large, broad villi that were
well-rounded on their distal ends. The bases were much
wider than those of other species. The height averaged
#05 microns and the height of the epithelium was.31 microns.
In appearance they resembled cylindrical haystacks with
a well-formed dome.

The shortest villi were found in the ox (Plate IX).
They.measured only 363 microns in height and had an epi-
thelial cell covering which.measured 22 microns., They.

'were slender and markedly constricted at their bases.
They were more numerous than they were in the horse and
hog.

These results disagreed somewhat with those of Ellen-
berger (1911). In order of decreasing.height of.villi he
listed the above animals in the following succession: cat,
dog, horse, pig, sheep, goat,.and ox. The findings of this
experiment indicated that although there was little differ-
ence in.the_height of the villi of the sheep, hog, and

horse, the order of succession was cat, dog, goat, sheep,

swine, horse and ox. Table 1 indicates the average measure-

ments .

TABLE. ‘1
COHPARISON 0.? .V ILLI

    

  

—mM‘~nw—-~ ._.__. ——- ————.__.._._

 

 

”my wzssm
(in microns) (in Morons)
Cat W 963 16
Dog 6‘5 32
Goat 615 28
Sheep #83 25
3°“ 1.70 29
Horse L05 31
°‘ 363 22

 

 

 

Thickness of the museularis mucosae. In all cases the
museularis mucosae was in two layers, an inner circular and
an outer longitudinal one. Except in the dog, these layers
were so narrow and incomplete it was impractical to measure
them separately. The combined layers ranged in thickness
from a low of 15 microns in the cat and goat to a high of
26 microns in the horse. In the dog, the muscularis
mucosae was markedly different. (Plate. X) It was in two
layers either of which was thicker than the combined layers

in the other species. The inner circular layer averaged

.39-

27 microns in thickness; the outer longitudinal layer
averaged M microns. The two layers totaled 71 microns
which is over three times wider than that of the average
of other animals. (Pig, Plate II)

These findings disagreed somewhat with those of Ellen-
berger (1911). He found that the museularis mucosae of-
the horse was thicker than that of the dog. In order of
decreasing thickness, his measurements in microns were as
follows: horse, 120; dog. 95.8; ox, 31.2; cat, 28.9; hog,
2h.2; sheep, 22.1; and goat, 20.

Brunner's glands. Brunner's glands were found in all
species but they were much more "extensive in some than in
others. In the horse they were found in the. first four
sections in all cases, and in one animal they were identi-
fied in the fifth section. As these sections were taken .
at every tenth segment of the tract, this indicatedthat
the duodenal glands extended down the tract as far as 32
feet from the pylorus.

In the dog, the opposite extreme was found. . In six
of seven dogs, no Brunner's glands were found in the sections
examined. in eighth dog was used. and sections from .various
segments of the duodenum were examined specifically for.
these glands. They were found only in the very proximal

part of the duodenum.

-h0-

In an attempt at finding the exact location of these
glands, longitudinal sections were taken beginning at the
pylorus and extending a short distance along the duodenum.
It was found that on the left side of thedigestive tube,
the glands extended. 2 mm. into the pylorus and. 2; mm. into
the duodenum. On the right side they extended 3/1. mm.
into the pylorus and 1% mm. into the duodenum. The total
extent of these glands was 1.; mm. or .18 inch on the left
side and 2}, mm. or .09 inch on the right side. This is
somewhat less than the 15 to 20 mm. found by Ellenberger
(1911).

In the ox, difficulty was also experienced inlecating
Brunner's glands. None were found in the sections of the
first six cow intestinal tracts examined. A seventh cow
was sacrificed and glands were located about one foot from
the pylorus. As these glands were found. scattered through-
out the first 12 to 15 feet of. the duodenum by. Sisson and
Grossman (1938), it is probable that they were present but
were dispersed thinly enough to .be missed when. sections
were taken only. every tenth distance.

In the other species, duodenal glands were readily w
found. In the pig they extended at least llt feet from the
pylorus. (In the cat, goat, and sheep they were found only
in the first section near the pylorus.

Two measurements were made on the Brunner's glands--

the diameter of the lumen and the height of the epithelium.

-41-
The Brunner's glands of the goat had the greatest lumen
diameter while those of the hog had the smallest. (Plate
III) The glands of the goat and the dog showed the highest
epithelium while those of the cat had the lowest. (Plate

XIII) Complete measurements are shown in Table 2..
TABLE 2

BRUNNER'S GLANDS

 

 

 

Species Lumen Diameter Height
(in microns) of Epithelium
.. (in microns)
Goat 50 35
Sheep ' L0 20
Dog 35 35
0x 25 12
Cat 20 p 10
Ikmse 7 15
Ehdne 3 25

 

 

 

The tunica muscularis. The outstanding difference in
the muscle layers of the various animals was an extra oblique
layer in the carnivores. In the other species, there were
distinct inner circular and outer longitudinal layers with
an.Auerbach's plexus between them. The carnivores had these
same two layers plus an oblique layer between the submucosa

and the circular layer. In the dog, this layer averaged

4,2-

1.7 microns in thickness and was easily identifiable in all
sections. (Plate XIV) In the cat, this oblique layer was
only 16 microns in thickness and was difficult to locate in
some sections.

The tunica muscularis was the thickest in the horse
where it reached an average thickness of 1153 microns. The
longitudinal layer of muscle was nearly as thick as the
circular layer. This differed from the other species where
the circular layer was much the largest of the two. (Pig,
Plate IV) Table 3 shows the average width of the museularis

mucosae and the layers of the tunica museularis.
TABLE 3

COMPARISON 01‘ MUSCLE

 

 

 

 

 

 

 

Tuni ca mscularie
Species Huscularis
Hue osae Oblique Circular Longitudinal Total
Layer Layer , Layer

Horse 26 -- 625 528 1153
Dog 71 #7 #27 227 701
Ox 19 -- 368 220 588
Get . 15 16 1111» 125 555
Reg 23 -- 332 188 520
Sheep 2h -- 175 112 287
Goat 15 -- 100 75 175

 

 

 

 

 

 

-43-

The measurements in Table 3 are in fairly close agree-
ment with those of Ellenberger (1911). He gave the followb
ing measurements in microns for the thickness of the tunica
‘muscularis of the jejunum; 'horse, 2070; dog, 1579; cat,
lh33; ox, 659; Pig, 263; sheep, 191; and goat, 157. The
discrepancy between his measurements and those in Table 3
is probably due to the state of distention of the intestines
at the time of the death of the animal.

Special connective tissue lazgg. In the dog, an extra
connective tissue layer was observed between the museularis
mucosae and the crypts of Lieberkuhn. (Plate I) This
zone of connective tissue was about 30 microns in thickness
and completely encircled the intestine. It was not observed

in any of the other animals studied.

Plate I Villi in the duodenum of a dog. 1001

 

Plate I

 

Plate II The flat Peyer's patch of the pig. 8]:

 

Plate II

 

Plate III The elevated Peyer's patch of the dog. 8X

 

-h6-
Plate III

 

Plate IV Tall, narrow villi of the cat. Hematoxylin
and eosin. 2501

Plate IV

 

Plate V Constricted, club-shaped villi of the dog.
Hematoxylin and eosin. 250x

‘ The serrations along their borders are
caused by their partly contracted state.

4.3.

Plate V

 

Plate VI Tall, constricted villi of the sheep.
Hematoxylin and eosin. 2501

Plate VI

.4

'.l

 

Plate VII Widely Spaced villi of the pig. Hematoxylin
and eosin. 250K

2m.

.AESOff

" ‘13 at:

w
b

-50.

Plato VII

”J

, L

’1
p '. O.r"!o.
.O‘Jvl. 11% :Jtl
. a 0. I x ‘ 5‘.r~
. .~./o“.u‘a

\

fl!

 

Plate VIII Broad based, rounded villi of the horse.
Hematoxylin and eosin. 250x

-51-
Plate VIII

 

Plate IX Short villi of the cow. Hematoxylin and
eosin. 2sz

Some of the villi show a branching.

Plate II

:1 ~" ‘
Y" ’ ‘
,3 ‘Y.’ r

flew .3727: I" y

 

Plate I. museularis mucosae of the dog.

Hematoxylin
and eosin. 760x

Note that it is canposed of an inner
circular and an outer longitudinal layer.

To the right of the inner circular layer is

the extra connective tissue layer peculiar
to the dog.

Plate X

 

Plate XI museularis MMcosae or the pig. Hematoxylin
and eosin. 7601

Note that it is a single narrow
layer. ‘

 

Plate XII Brunner's glands. Hematoxylin and eosin.
1501

Fig. l Hog. Note the narrow lumen
diameter.

Fig. 2 Goat. Note the very wide lumen
diameter 0

Plate XII

 

Fig. 2

Plate XIII Brunner's glands. Hematoxylin and eosin.
750K

Fig. 1 Cat. Very low epithelium.
Fig. 2 Goat. Very high epithelium.

-56-
Plate XIII

 

Plate XIV Tunica museularis of dog. Hematoxylin
and eosin. thX

Note the narrow oblique muscle layer
next to the submucosa.

Plate IIV

 

Ii.

er?

4,.) x.
37.9... _ 5 ‘1. _ . . ..
, . ‘p. , .4 .Tgflel . ... I Ax . ._ .

. . _ o J . .. D. s. .o 3 .
_. _ iv .. ,. .33.. 1? L
, 2L . 9 ....\.ar.w .. ,
. . . ..v.

r v . . y u.
. .. ' J. ., ¢ .... .3
. . I

._

52...”

. .

.5. f
y It:.I‘o..C 1..

 

Plate XV Tunica museularis of pig. Hematoxylin
and eosin. lhOX

Typical inner circular and outer
longitudinal muscle layers.

n
O
t
a
1
P

‘

. x

O x ‘ §

. :3 Xx. ..
‘ \ \. J \ .. \\ ‘\
. ’ 445;.» .
a ‘A‘. e
._ e \.T.
o ‘ .

II

\

 

SUMMARY AND CONCLUSIONS

The small intestines of 39 animals representing seven
different species were compared grossly and microscopically.
A gross examination revealed that .the small intestine of
,the horse contained the greatest number..of Peyer's patches,
approximately 85 per animl. The Peyer's patches of the
cat were too small to be seen grossly but were found in
microscopic section. Those of the dog were the easiest to
identify for they were quite evident as thickened elevations
even on the exterior of the intestinal tract. Patches in
other animals were flat and could be seen only on the interior
surface. Most patches were located opposite the mesentery
except in the dog where they usually assumed a position on
the lateral and medial sides of the gut tube. They were
found in the JeJunum and ileum of all species studied, and
in the dog, were found in the duodenum as well. Most histo-
logy texts used by veterinary students are written from. a
study of human subjects and infer that Peyer's patches are
found only in the ileum. This is not true as far as domestic
animals are concerned.

Intestinal villi were longest in the cat. Measurements
revealed that they averaged 963 microns in height in the cat
as compared to 61.5 in the dog, 615 in the goat, 1.83 in the

~60-
sheep, A70 in the hog, #05 in the horse, and 363 in the ox.
The height of the epithelial cells on the villi was greatest
in the dog (32 microns) and least in the cat (16 microns).
no significant difference in the villi height was noted at
different levels of the tract.

Shapes of villi ranged from.broad and rounded in the
horse to very tall and narrow in the cat. All species
except the horse showed a distinct narrowing of the villi
at their bases. Villi of the carnivores were expanded on
their distal ends. No differences in the shapes of the A
villi at different levels of the tract were noted.

The.musoularis mucosae was very narrow in all the
species studied except in the dog where it was found to be
in two distinct layers either of which was thicker than the
[museularis mucosae in the other species. It was approxi-
mately three times thicker than the general over-all
average of the other animals studied.

Brunner's glands differed widely both as to extent and
form. They were very rare in the dog and, in the sections
studied, were found at the pyloric-duodenal Junction extend-
ing over an area of less than l/5 inch. In the sections
taken they were found in only one cow of seven studied.
Sisson and Grossman (1938) found that they were scattered
throughout the first 12 to 15 feet of the intestine of this
species. In the light of this knowledge, it is thought

-61-
probable that Brunner's glands are rather thinly dispersed
in the cow and are easily missed upon microscopic.section.

They were found in the Jejunum as far as 32 feet from
the pylorus in the horse and were rather extensive in all
sections in the first 25 feet. In the cat, sheep, goat, and
pig, they were readily identified in the proximal part of
the intestine. Human histology texts describe Brunner's
glands only in the duodenum. I

The lumen of the Brunner's glands varied from a high
of fifty.microns.in the goat to a low of three microns in
the hog with the sheep, dog, ox, cat, and horse falling
between them in that succession. Epithelial cell height
on the glands was highest in the dog and goat and lowest in
the cat.

The muscle layer varied considerably. It was thickest
in the horse where it averaged 1153 microns in width and
thinnest in the goat with an average of 175 microns. The
carnivores had an extra oblique layer of muscle between the
submucosae and the circular layer. In order of decreasing
'width of tunica museularis, the succession of animals was
found to be horse, dog, ox, cat, hog, sheep, and goat..

Table b shows various comparisons in the species studied.

-62-

 

 

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,
*,‘.-‘ t

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