A GROSS. HISTGLOGEC AND HI$TOCHEMECAL STUDY QF THE EYE ADNEXA OF $HEEP ARE? GGA'ES Thests {or the Degree of DB. D. MICHIGAN STATE UNEVERSETY Ram Das Sinha 1965 THESIS This is to certify that the thesis entitled A Cross, Histologic and Histochemical Study of the Eye Adnexa of Sheep and Coats. presented by Ram Das Sinha has been accepted towards fulfillment of the requirements for __li_D_ degree in Anatomv fiat? Mm . Major professor Date January 26, 1965 0-169 LIBRARY Michigan State University z:——/)7 to the head 01 dwe‘fe us ABSTRACT A GROSS, HISTOLOGIC AND HI STOCHEMICAL STUDY OF THE EYE ADNEXA OF SHEEP AND COATS by Ram Das Sinha As a result of the increasing importance of experimental ophthalmology and inadequate knowledge of the gross anatomy, his- tology and histochemistry of the eye adnexa of sheep and goats, the present investigation has been undertaken. For the histologic study, the eye adnexa of 8 male sheep, 2 weeks to 5 months old; 8 female sheep, 3 months to 4 years old, and 4 male goats, 5 days to 5 months old were obtained. In addition to the heads of these animals, 4 heads of female sheep, 3 to 4 years old were used for the gross anatomy. For histochemical study frozen specimens from 2 sheep, 2 months to 2 years old and Z goats, 5 days old, and in addition, paraffin sections from all the animals used for histology were processed. Ten percent formalin fixed and latex injected specimens were dissected for gross study. For the study of the course of the lacrimal drainage passage and orbital blood vessels, injections of radiopaque substance (barium sulphate) were employed. For the detailed study of the blood vessels of the adnexa, India ink injection technique was used. The following stains were used for the histologic study: (1) Harris hematoxylin and eosin, (Z) Weigert and Van Gieson's stain, (3) Mallory's triple stain, (4) Gomori's reticular stain, and (5) Modified Bielschowsky Gros silver stain. Ram Da 3 Sinha For the histochemical study paraffin sections were stained with (1) Alcian Blue and Nuclear Fast Red, (2) Toluidin Blue and (3) Periodic acid Schiff (PAS) reagent. Frozen sections were treated with (4) Sudan Black, (5) Nile Blue Sulfate, (6) Naphthal As-Bl and Phosphoric acid and (7) Naphthal As-Mx and Phosphoric acid. The following observations were made in the eye adnexa of sheep and goats: Eyebrows are represented by a few supercilia and some sensory hairs. The medial palpebral commissure of sheep is unpig- mented and grooved leading to the lacrimal (infraorbital) pouch which contains large multilobulated sebaceous glands. The lacrimal pouch is absent in goats. Muscles of Miiller and Riolan are well developed. The conjunctival epithelium is variable being stratified squamous at some places, stratified cuboidal to columnar at other places and occasionally transitional. Goblet cells and varying number of lympho- cytes and lymph nodules are present in the conjunctiva. Lymph nodules are more numerous in sheep. The post-tarsal conjunctiva of goats contains epithelial “buds. " The limbal conjunctiva lacks Manz glands but always contains an epithelial thickening, a few rete pegs and some pigment granules. The caruncles of sheep are microscopically similar to those of goats. The deep nictitans (Harderian) gland is absent in both. The superficial nictitans gland is a mixed gland: tubuloalveolar in sheep and compound tubuloalveolar in goats. The PAS reagent and Alcian Blue reveal the presence of mucous and serous glands The periorbita, orbital fascia and extrinsic ocular muscles are similar. Microscopically the lacrimal glands resemble the nictitans glands. Many plasma cells are present in the nictitans and lacrimal glands. Six or seven lacrimal excretory ducts are present in both and are lined with stratified columnar epithelium having many goblet cells I . . V. v. x. .6 Z; .G r . H” n.” .: Ll“ .Fu ah. .“ vflm . . .3 . ,L . .....\ 6; .P. ‘ a W. .3 an an «I .4 n: "u r“ fl» his . .|\ v i v '4 "‘V“ s¢4u4£ ’n QKQA ep' Ram Da 5 Sinha in both species. Connective tissue septa of the lacrimal gland of sheep contain some smooth muscle fibers. Lacrimal canaliculi are lined with stratified squamous epithelium near the puncta and stratified columnar near the lacrimal sac. Lacrimal sacs and nasolacrimal canals are generally lined by stratified columnar epithelium containing varying numbers of goblet cells. At some areas pseudostratified epithelium is also observed. They are surrounded by a rich venous plexus. The lower third of the nasolacrimal ducts is surrounded by s e romucous gland s. A GROSS, HISTOLOGIC AND HISTOCHEMICAL STUDY OF THE EYE ADNEXA OF SHEEP AND GOATS By Ram Da 8 Sinha A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Anatomy 1965 VITA Ram Das Sinha Candidate for the degree of Doctor of Philosophy Final Examination: January 13, 1965. 9:00 a.m. Dissertation: A Cross, Histologic and Histochemical Study of the Eye Adnexa of Sheep and Goats. Outline 5 of Studie s: Major Subject: Anatomy Minor Subjects: Physiology and Surgery and Medicine Bioggraphical Items: Born: January 2, 1927. Parents: B. Bishundhari singh and Smt. Dhanmato kunwar. Chamanbigha, Jehanabad, Gaya, Bihar, India. Undergraduate Studies: I. Sc., Science College, Patna, 1948. G. B. V. C. , Bihar Veterinary College, Patna, 1951. Graduate Studies: M. S., Michigan State University, 1964. Experienc e s: Touring Veterinary Surgeon, 1951. Demonstrator in Anatomy, B. V. College, Patna, 1951-1954. Lecturer in Anatomy, B. V. College, Patna, 1954-1962. Assisted in teaching Anatomy, M. S. U., 1962-1963. Research, Michigan State University, 1962-1965. Editor (Hindi section) “Bihar Veterinarian, " 1958-1962. Member of: Bihar Veterinary Association and Phi Zeta (a national honor society of Veterinary Medicine) ii . er- .n'u A Or.- a .‘n.L—‘" 0.. ~-—$~ A .....C‘-u. v ‘- A .: -IVV‘V'v-\ - 4..¢e.¢. C ACKNOWLEDGMENTS The author wishes to express his deep and sincere appreciation and thanks to Dr. M. Lois Calhoun, Professor and Head of the Department of Anatomy and Chairman of the Guidance Committee, for her constant supervision, guidance and encouragement throughout the course of the investigation and higher studies. He wants to record his grateful thanks to Dr. C. W. Titkemeyer, Dr. T. W. Jenkins, Dr. R. Brown, Dr. E. M. Smith, Dr. A. W. Stinson, Mr. R. Carrow, and Dr. E. H. Roege for their continuous suggestions, inspiration and help. He is grateful to Dr. W. D. Collings, Professor of Physiology and Pharmacology, and Dr. G. H. Connor, Professor of Surgery and Medicine for sparing their valuable time for serving on the Guidance Committee and giving valuable advice. The writer wishes to thank Dr. R. A. Fennell, Professor of Zoology for his help and advice in histochemical preparations and Dr. U. V. Mostosky, Assistant Professor of Surgery and Medicine for his help in radiography. Special thanks are extended to Mrs. Jan Sharon and Mr. Carl Oehling for their technical assistance, Mrs. Luella Wahl and Mrs. Mae Suit, secretaries, for their typing assistance, and all members of the Anatomy Department and friends for their beneficial suggestions. Finally, the author's sincere gratitude goes to his wife Smt. Phulmati Devi, his brothers: Sri Ram Dahin Singh and Sri Ram Prasad Singh, and the officials of the Government of Bihar, India for their enthusiastic inspriation and help in diverse ways to make this higher education a reality. '1! f'l O ‘ .fi. :v ('1 (I) 4'" c .4 .4 ('TE m; A b—A TABLE OF CONTENTS Page INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . 1 REVIEW OF LITERATURE . . .. . . . . . . . . . . .. . . . . 2 Eyebrows . . . . . . . . . . . . . . . . . . . . . 3 Eyelids (Palpebrae) . . . . . . . . . . . . . . . . . .. . 3 Conjunctiva . . . . . . . . . . . . . . . . . . . . . . 9 Lacrimal Caruncle (Caruncula lacrimalis) . . . . . . . 12 The Third Eyelid (Nictitating Apparatus) . . . . . . . . 12 Periorbita (orbital periosteum) . . . . . . . . . . . . . 16 Orbital Fascia. . . . . . . . . . . . . . . . . . . . . . 17 Extrinsic Ocular Muscles . . . . . . . . . . . . . . . . 18 The Lacrimal Apparatus . . . . . . . . . .. . . . . . . 20 Lacrimal Gland . . . . . . . . . . . . . . . . . . 20 Lacrimal Excretory Ducts . . . . . . . . . . . . 22 Puncta lacrimalia . . . . . . . . . . . . . . . . . 23 Lac rimal canaliculi . . . . . . . . . . . . . . . . Z3 Lacrimal Sac . . . . . . . . . . . . . . . . . . . 23 Nasolacrimal Duct . . . . . . . . . . . . . . . . Z4 MATERIALSANDMETHODS................. 25 Source of Animals. . . . . . . . . . . . . . . . . . . . 25 Technique . . . . . . . . . . . . . . . . . . . . . . . . 25 Measurements . . . . . . . . . . . . . . . . . . . . . . 27 RESULTSANDDISCUSSION.................. 28 Eyebrows . . . . . . . . . . . . . . . . . . . . 28 Eyelids (Palpebrae). . . . . . . . . . . . . . . . . . . 28 Conjunctiva . . . . . . . . . . . . . . . . . . . . . . 37 Lacrimal Caruncle (Caruncula lacrimalis) . . . . . . . 42 Third Eyelid (Nictitating Apparatus) . . . . . . . . . . 42 Periorbita (orbital periosteum) . . . . . . . . . . . . . 46 OrbitalFascia... 47 Extrinsic Ocular Muscles . . . . . . . . . . . . . . . . 47 Lacrimal Apparatus . . . . . . . . . . . . . . . . . . . 48 Lacrimal Gland . . . . . . . . . . . . . . . . . . 48 TABLE C PLAT ES SL’MMAR LITERAl TABLE OF CONTENTS — Continued Lacrimal Excretory Ducts . . . Puncta lacrimalia. . . . . . . . Lacrimal Canaliculi . . . . . . Lacrimal Sac . . . ....... Nasolacrimal Duct . ..... PLATES........ SUMMARY ...... . LITERATURE CITED . . o a n o a u o n a a a ooooooooooo oooooooooo o a a o nnnnnnnnn a I o o aaaaaaaaa nnnnnnnnn ooooooooo Page 50 51 52 55 113 115 PLAT E 11 PLATE II. III. IV. VI. VII. VIII. XI. XII. X III. XIV. XV. . Eye of sheep: LIST OF PLATES external adnexa ............ Diagram of the vertical section of the eye of sheep: specimen areas and related structures ........ Diagram of the horizontal section of the eye of sheep: specimen areas and related structures ........ Diagram of the lac rimal apparatus of sheep: specimenareas. . . . . .. .. . . .. . Blood supply to the eye of sheep (Radiograph) . . . . (a) Blood supply in the eyelids and eye muscles of sheep (Radiograph), (b) Lacrimal passage of sheep (Radiograph)...................... Blood supply to the eyelids of sheep (India ink injected). . . . . . . . Blood supply to the lacrimal gland of sheep (India ink injeCted) . O C C O O O O O O C O O O O C O Skeletal muscle fibers inserting in the skin of the eyebrow of the sheep ........ . . ....... Eyebrow of the goat. Tarsal glands of the upper eyelid of sheep . . . . . . Skeletal muscles arrangement in the upper eyelid of the goat . Ciliary follicle of the lower eyelid of sheep . . . . . Lower eyelid of sheep. ......... . ..... . Glands of Moll in the lower eyelid of sheep ..... vi Page 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 l 1 115.1 01 PLATE XVI. XX XX] XXI XXI XX XX XX\ XXV XX X): XX: XXX LIST OF PLATES - Continued PLATE XVI. Muscle of Miiller ending in elastic fibers in the lowereyelidofsheep. . . . . . . . . . . . . . . . . XVII. Tactile hair of the lower eyelid of the sheep . XVIII, Lacrimal (infraorbital) pouch glands of sheep. XIX. Upper palpebral marginal conjunctiva of sheep XX. Upper palpebral tarsal conjunctiva of sheep . . XXI. Upper palpebral tarsal conjunctiva of the goat . . . . XXII. Upper palpebral post-tarsal conjunctiva and lacrimal excretory duct of sheep. . . . . . . . . . . XXIII. Fornix conjunctiva of sheep (Alcian Blue Stain) . . XXIV. Fornix and lower palpebral post-tarsal conjunctivae ofsheep........................ XXV. Reticular fibers in the fornix and lower palpebral post—tarsal conjunctivae of sheep. . . . . . . . . . . XXVI. Limbal conjunctiva of sheep . . . . . . . ...... XXVII. Bulbar and limbal conjunctivae of the goat . XXVIII. Lacrimal caruncle of sheep. . . . . . . . . . . . . . XXIX. Membrana nictitans of sheep . . . . . . . . . . . . . XXX. Membrana nictitans of the goat . . . ..... XXXI. Nictitans gland and fornix conjunctivae of sheep . XXXII. Nictitans gland of sheep (Alcian Blue Stain) XXXIII. Nictitans gland with excretory duct of sheep . . . . . Vii Page 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 LIST OF PLATE xxxw. xxxv.: XXXVI. xxxvu. xxxvm. XXXIX. XL. nu. X1111. XLIV, XLV, XLVL XLVH. XLVHI 41 LIST OF PLATES - Continued PLATE XXXIV. XXXV. XXXVI. XXXVII. XXXVIII. XXXIX. XL. XLI. XLII. XLIII. XLIV. XLV. XLVI. XLV II. XLVIII. XLIX. L0 L1. LII. LIII. Nictitans gland of sheep: (PAS reagent) . . . . . . . Nictitans gland with excretory duct of the goat. Nictitans gland of the goat (PAS reagent) . ...... Periorbita and orbital septum of sheep. . . . Bulbar fascia (Tenon's capsule) of sheep. . . . . . . Lac rimal Lac rimal Lac rimal Lac rimal Lac rimal Lacrimal Lac rimal Lac rimal Lac r imal Lac rimal Lac rimal Lac rimal Lac rimal Lac rimal gland and smooth muscle of sheep . . . . . gland of sheep, (Alcian Blue Stain) . . . . gland of sheep, (PAS reagent) . . . . gland of the goat, (PAS reagent) . . . . . glandofthegoat................ excretory duct origin in sheep . . . . . excretory duct of sheep (PAS reagent). . . excretory duct of sheep . . . . . . excretory duct of the goat . . . . . . . . . canaliculi of sheep . . . . . . . . . . . . . sac of sheep (Pigment cells) . . . . . . . . sacofsheep ..... . . ..... sac of sheep (Alcian Blue Stain) . . sac and nasolacrimal duct of sheep . . . . Nasolacrimal duct and lacrimal pouch gland of sheep viii Page 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 LIST OF PLATE 1.1121 W. L UT. “11. U’lll. LIST OF PLATES - Continued PLATE LIV. Nasolacrimal duct of sheep: Midportion (PAS re- agent) 9 o e o o oooooooo o o o o o o o o o o o 0 LV. Nasolacrimal duct of sheep: Midportion ....... LVI. Nasolacrimal duct of sheep: Distal portion ..... LVII. Nasolacrimal duct of the goat: Proximal portion . . LVIII. Nasolacrimal duct of the goat: Midportion ix Page 108 109 110 111 112 {3 a, (II ‘1 f1 1‘ m able by anima: aCCess INTRODUCTION The present investigation on the eye adnexa of sheep and goats was undertaken for many reasons: The importance of veterinary Ophthalmology is increasing rapidly. The recent investigations of Catcott (1952), Magrane (1951, ‘55, '57, ‘59), Smythe (1956) and others have given impetus to this area of research. Sound knowledge of ocular anatomy provides a basis for a better understanding of ocular physiology, pathology and clinical medicine and surgery. Extensive literature on the anatomy of the human eye is avail- able but comparatively little work has been done on the eye of domestic animals, especially sheep and goats. Occurrence of eye cancer is generally found associated with the accessory structures of the eye such as eyelids, nictitating membrane, caruncle and conjunctiva. There is a considerable controversy regarding the presence or absence of the following structures in various mammals: the Harderian gland, the smooth muscle fibers in the nictitating membrane and the Manz glands of the conjunctiva. Among laboratory animals used for experimental ophthalmology, the sheep is unique in that its lacrimal artery can be approached with- out entering the orbit. While the chemical nature and functional activities of the ocular glands of many laboratory animals and man have been examined histo- chemically, no similar technique has been applied to the eye of sheep and goats . Ar. 4 f 0‘ . ,. 0‘ Lite C31 2&0me . t '1 m' m REVIEW OF LITERATURE An extensive survey of the literature revealed that knowledge of the comparative anatomy of the eye of domestic animals is still incomplete. Standard books of veterinary anatomy include very little information on the gross and microscopic structures of the eye of sheep and goats. In “The Anatomy of Domestic Animals“ by Sisson and Grossman (1953), a complete description of the eye is given only for the horse and comparatively little or none for the other domestic animals. Even specific books like "Anatomy and Histology of the Eye and Orbit in Domestic Animals" by Prince e_t a__._1. (1960) and "Fundamentals of Histology of Domestic Animals” by Trautmann and Fiebiger (1957) are insufficient regarding the eye adnexa of sheep and goats . EYEBROWS Gross - Eyebrows are not confined to the primates only. Cat eyebrows are represented by a few long hairs. In man, the space between the two eyebrows usually remains smooth and hairless and hence called glabella (Wolff, 1955). Human eyebrows are transversely arched eminences of skin surmounting the orbit and supporting numer— ous, short, thick and comma shaped hairs (Boyd, 1956; Johnstonet aLI. 1958). Their muscles are innervated by the facial nerve (Berens and Siegel, 1950). . Histology - In structure, the human eyebrows resemble the hairy scalp. The skin is thick, mobile and richly supplied with sebaceous glands. Fibers from the oricularis oculi, corrugator and occipito- frontalis muscles are inserted into the skin of the eyebrows (Boyd, 1956; Johnston _e_t a_l., 1958). gr“ -. p opp ‘ . .Leab 1 .H' guy '7‘ 0 U V E retec“ D C‘ Q‘xr9‘ 5“. L. we '05 c. .0. A u .C .C EYELIDS (PALPEBRAE) M - Eyelids are present only in vertebrates. Except in some sharks, fishes lack eyelids or have only rudimentary immobile lids (Romer, 1962; Wolff, 1955). In amphibia the upper lid is immobile while the lower one is movable (Prince, 1956). In terrestrial animals the lids are better deve10ped for cleaning and moistening the cornea, protecting the eyeball from external injury and helping the pupil to regulate the amount of light reaching the retina (Boyd, 1956). In reptiles there are many varieties of lids, thick and slightly mobile in cheleonians (turtles, tortoise), thin and usually the lower one mobile in lizards and a transparent movable lower lid in serpents. In birds the lower eyelid is far more mobile than the upper one (Wolff, 1955), but in mammals the reverse is true (Prince, 1956). The upper lid is shorter in cats and longer in horses. The eyelids of the ox are quite thick and tougher than those of horses. In sheep they are comparatively thinner than those of swine and goats (Prince, 1956; Prince e_t a1. , 1960). Gross anatomy of the eyelids has been described by Chauveau (1891), Ellenberger and Baum (1943), Prince e_t 341. (1960) and Sisson and Grossman (1953) in various domestic animals. Both lids are united on either side by corresponding lateral and medial palpebral commis- sures. The interval between the margins of the lid is called palpebral fissure or Rima palpebrum (Sisson and Grossman, 1953). The palpebral fissure of birds is circular (Nicolas, 1924). The ends of the fissure form corresponding lateral and medial angles or (£13111. The lateral canthus is acute when the eye is opened, while the medial canthus is narrow and presents a depression called the lacrimal lake (I;a_c_1§ lacrimalis) which lodges a small rounded pigmented eminence called lacrimal caruncle (caruncula lacrimalis). Each lid consists of two surfaces, external or cutaneous and internal or palpebral and a free border (Sisson and Grossman, 1953); Wolff, 1955). The free border near the medial canthus presents a small papilla on which Opens the Punctum lacrimalis. This border consists of two margins, anterior and posterior known as Limbus palpebralis anterior and posterior respectively. The anterior margin carries the eyelashes or cilia (Sisson and Grossman, 1953). Each lid is composed of the skin, subcutis, muscular layer, tarso-fascial layer and palpebral conjunctiva (Sisson and Grossman, 1953; Trautmann and Fiebiger, 1957). The skin is freely movable except at the free border and is covered by a dense coat of fine hairs and few tactile hairs (Prince e_t a_:_1. , 1960; Sisson and Grossman, 1953). Tactile hairs are found scattered at the base of the lower lid of the horse (Prince e_t a_t_l., 1960), on the eyelids of the fetal pig (Fowler, 1962), on both eyelids of sheep (Prince e_t a_l., 1960) and goats (Prince e_t £11., 1960; Sar, 1963). In swine the palpebral skin contains coarse and widely scattered hairs (Trautmann and Fiebiger, 1957). The skin of the free border is smooth and usually pigmented (Prince it a_._1., 1960). Eyelashes are longer in the upper lid. Cilia of the lower eyelid are lacking in carnivores and swine (Trautmann and Fiebiger, 1957). Cilia of the upper lid number about 100 in horses and cattle and 30 in asses while the lower eyelid contains about 60 in cattle and 25 in asses (Prince e_t a_l. , 1960). In birds the rudimentary feathers without barbs take the place of the eyelashes and tactile hairs (Nicolas, 1924). The subcutis is devoid of fat and intermingled with the muscular coat (Trautmann and Fiebiger, 1957). The palpebral muscles vary in number and arrangements from one species to another. The orbicularis oculi is constantly found in all domestic animals (Sisson and Grossman, 1953). It is an elliptical muscle surrounding the palpebral fissure and attached laterally and medially by palpebral ligaments. At the medial commis sure a slip is detached detached from the orbicularis oculi which passes medially behind the lacrimal sac and attaches to the orbital wall and is known as Pars lacrimalis or Harner‘s muscle (Prince e_t a_l., 1960; Sisson and Grossman, 1953). Other palpebral muscles which are constantly found are the aponeurosis of the levator palpebrum superioris in the upper lid and an aponeurotic slip of the inferior rectus in the lower lid. Both of these muscles are attached to the posterior part of the corres- ponding tarsi (T rautmann and Fiebiger, 1957). In addition to these muscles, the orbicularis oculi. receives fibers from the corrugator supercilii in the horse and dog, and frontalis in the ox in the upper lid, and malaris in the lower lid. The malaris muscle is absent in pigs (Sisson and Grossman, 1953). The tarso-fascial layer consists of an anterior fibrous plate (the tarsus) and the posterior fibrous membrane (the palpebral fascia or orbital septum). Human tarsi are semilunar in shape and the superior tarsus is larger than the inferior one (Woodburne, 1957). The ends of the tarsi are attached laterally and medially to the orbital wall by the lateral and medial palpebral ligaments respectively (Prince e_t a_._l., 1960) and the convex borders of the tarsi are attached to the orbital septum (palpebral fascia) which is continuous with the periosteum at the superior and inferior margins of the orbit (Woodburne, 1957). Tarsal glands are embedded in the deep face of the tarsus and are arranged vertically to the free margin of the lids and parallel one another (Sisson and Grossman, 1953). The palpebral conjunctiva lines the internal surface of the lid and attaches firmly to the tarsus (Bedrossian, 1958). The blood supply to the eyelid of the horse comes from the branches of the ophthalmic and facial arteries and the blood is drained by corresponding veins (Sisson and Grossman, 1953). In man, the eyelids are supplied by the branches of both facial and ophthalmic arteries but in most animals chiefly by the malar artery which is a branch of the infra-orbital artery (Prince and Ruskell, 1960). l Lymph vessels of the eyelids of the ox drain to the parotid lymph node (Sisson and Grossman, 1953). The sensory innervations to the struc- 4 tures of the eyelids are derived from the ophthalmic and the maxillary 3 divisions of the trigeminal nerve. The motor nerves to the orbicularis I oculi come from the facial nerve. The levator palpebrum superioris is supplied by the oculomotor nerve. The smooth muscle fibers (muscle of Miiller) are innervated by sympathetic fibers (Prince e_t 3L1" , 1960; Sisson and Grossman, 1953). Human eyelids develop as folds of integument adjacent to the eyeball (Arey, 1954). At the beginning of the second month each of the folds remains circular and hence the palpebral fissure is first rounded. After two weeks the upper and loWer portions of the folds grow towards each other and thus angles (91133111) are formed and the upper and lower eyelids are demarcated. Their edges meet and fuse loosely. At about the fifth month the epidermal union starts to separate through keratinization. of cells and becomes completely separated at the seventh or eighth month (Wolff, 1955). In some mammals it is delayed until after birth (Arey, 1954). The cilia of rats (Fowler, 1962), and of men (Arey, 1954; Wolff, 1955) develop like ordinary hairs as epithelial buds from the fused lid margins, first on the upper lid and then on the lower lid. Glands of M011 and Zeis develop as outgrowths from the ciliary follicles. The tarsal (Meibomian) glands develop as ingrowths of a regular row of solid columns of ectodermal cells from the lid margins behind the posterior row of cilia (Wolff, 1955). Histology - The palpebral epidermis of man contains all four layers (Wolff, 1955). In rats the epithelium is thin which becomes thick at the margin (Holmes, 1960). The stratum corneum is thin and the stratum germinativum is one layer thick in swine (Marcarian, 1962). Abundant pigment granules are found in and between the cells of the stratum germinativum in cattle (Sinha, 1964). The dermis contains fine elastic and collagenous fibers in cattle (Sinha, 1964) and abundant elastic fibers and chromatophases in man (Bedrossian, 1958). The ordinary palpebral hairs are fine and are supplied with well developed sebaceous and tubular glands in Holstein cattle (Sinha, 1964). These hairs lack arrectores pilorum muscles in the rat (Holmes, 1960). Zeis glands are rudimentary sebaceous glands which open in the follicles of the eyelashes. Glands of Moll are modified sweat glands, some of which Open in the ciliary follicles and others in front of the openings of the tarsal glands as tiny orifices (Prince gt a_._l. , 1960). Tactile hairs lack arrectores pilorum muscles (Trautmann and Fiebiger, 1957). The subcutis is fat-free and contains loose areolar tissue (Wolff, 1955). The epithelium of the ciliary follicle in cattle becomes thickened near the nerve plexus (Goldsberry, 1965). The muscle fibers of the orbicularis oculi are arranged in a concentric manner and at the palpebral margin some of them,which enclose the ducts of the tarsal glands,and ciliary follicles and the associated glands are known as muscle of Riolan (Prince e_t a_l. , 1960). They are distinctly marked in cattle (Sinha, 1964; Trautmann and Fiebiger, 1957). Some smooth muscle fibers (Miiller' 3 muscle) are also found attached to the tarsus (Prince gt a_l. , 1960; Sinha, 1964). The tarsus is less developed in domestic animals than in man. It is composed of dense collagenous tissue and is fused with the capsule of the tarsal gland. In the pig there is a secondary fibro- cartilagenous tarsus near the base of the lid (Trautmann and Fiebiger, 1957). The tarsus of man also contains some elastic fibers (Wolff, 1955). The lower lid of most birds except parrots contains a saucer- shaped cartilage (Nicolas, 1924). The tarsal (Meibomian) glands are of the Cl RUSQIOL‘. -’ the largest of the modified sebaceous glands. They Open independently of the cilia on the ventral aspect of the lid margins. They are more numerous in the upper lid and variable in different species. Each gland has a central duct lined by simple cuboidal epithelium and is surrounded by numerous alveoli which open into it (Prince e_t a_l. , 1960). The main ducts as well as the alveolar ducts are lined with stratified squamous epithelium in cattle (Sinha, 1964). The glands are larger in the upper lid than in the lower one. The secretion of the gland is fatty in nature which lubricates and smoothens the margin and prevents the overflow of tears (Trautmann and Fiebiger, 1957). In the rabbit, guinea pig, cat, dog, horse and primates, the sebaceous parenchyma of the Meibomian glands is surrounded by a plexus of nerve fibers which contain specific cholinesterase (Montagna and Ellis, 1959). The Meibomian glands in birds are absent and their place is taken by a pair of Harderian glands (Nicolas, 1924). Histochemistry helps greatly to reveal the localization of chemi- cal constituents within cells (Lazarow, 1962). Sweat glands in the bovine species are negative for fat lipids or cholesterol and their esters, whereas sebaceous glands are positive for these lipids and their esters. Bovine sweat glands do not contain glycogen and lipids which are present in human eccrine and apocrine sweat glands (Yang, 1952). Using histochemical stains, Ato (1961a, b) and Sinha (1964) found that sweat glands of cattle are apocrine. The presence of alkaline phosphatase and phospholipids in sebaceous glands was re- ported by Montagna and Hamilton (1947) in the hamster, by Montagna and Noback (1947) in rats and by Montagna e_t a_l. (1948) in man. The saccules of the Meibomian glands are filled with a fatty epithelium. The amount of secretion is so slight that only histochemical methods are suitable to investigate it (Krause, 1934). According to Krause, Pes (1898) reported that the secretion of the Meibomian gland contains mostly cholesterol mixed with a small quantity of fat and soaps caused by the action of alkaline tears on fat. Buschke (1905) increased the glandular secretion by means of eserine and obtained a milky emulsion of fatty substance and tears. He observed the secretion as a thick mass in the alveoli and tubules which gave a partial reaction of fat. CONJUNCTIVA Gross - The conjunctiva is a thick transparent mucous mem- brane lining the eyelid as the palpebral conjunctiva and reflecting upon the anterior part of the eyeball as the bulbar conjunctiva. The line of reflection is called the fornix conjunctivae (Sisson and Grossman, 1953). The palpebral conjunctiva is extended to cover the caruncle and membrana nictitans (Smythe, 1956). It may be further divided into the marginal, tarsal and orbital parts (Wolff, 1955). The palpebral conjunctiva is firmly attached to the tarsal plate while the bulbar conjunctiva is loosely attached to the underlying structures and thus the conjunctiva helps in the suspension of the eyeball anteriorly (Prince (it 341. , 1960). The conjunctiva of the fornix is loosely attached and supero-laterally pierced by the orifices of the lacrimal excretory ducts (Prince e_t a__l. , 1960). The ocular epithelium which lines the anterior part of the eyeball is subdivided into the sclerotic and corneal parts. The corneal part is purely epithelial and is regarded as the anterior layer of the cornea (Smythe, 1956). The conjunctiva covering the margin of the cornea is known as the sclero-corneal or conjunctival limbus (Nicolas, 1924). The bulbar conjunctiva at the sclero-corneal junction contains pigment (Sisson and Grossman, 1953). The conjunctiva develops from the ectoderm lining the inner surface of the lids, front half of the sclera and the entire cornea (Arey, 1954). The blood supply to the conjunctiva comes from the anterior ciliary artery (Prince and “T" - Arte C'VAI -:: ,. 7“ C1.€t e... p O"l~\ 9r. o‘y'otn Al. Ruskell, 1960). A lymphatic system is also present in the conjunctiva. The conjunctiva is innervated by the branches of the fifth cranial nerve. The corneal part is supplied by the ciliary nerves which are the efferent branches of the ciliary ganglion and contain sensory fibers from the ophthalmic division of the fifth nerve (Symthe, 1956). Histolog — The conjunctiva consists of two layers: the epithelium and substantia propria. The epithelium at the lid margin is stratified squamous. The number of squamous cells and cell layers is reduced behind the lid margin. At the tarsal region the conjunctiva is reduced to two layers of cells, superficially columnar and deeply cuboidal a_- (Prince gt a_l., 1960; Wolff, 1955). The palpebral conjunctiva of the horse is papillated and contains many goblet cells (Sisson and Gross— man, 1953). At about the level of the tarsal glands the epithelium changes from stratified squamous to stratified columnar in the horse and carnivores or to transitional in the ruminants and swine (Trautmann and Fiebiger, 1957). The palpebral conjunctiva in man contains glands of Wolfring and glands of Henle (Wolff, 1955). The tarsal conjunctiva of the lower lid contains more cell layers. In the con— junctival epithelium at the fornix, a thin layer of polyhedral cells is added between the two cell layers and goblet cells increase in number (Prince e_t a_l., 1960). Only the horse has glands in this region (Trautmann and Fiebiger, 1957). The epithelial layers of the bulbar conjunctiva gradually increase to the limbus. The superficial cells become flatter and the deep ones cuboidal (Prince e_t a_l., 1960). At the limbus the epithelium is always pigmented (Trautmann and Fiebiger, 1957). The glands of Manz are saccular and are found at the limbus of the pig, ox, lamb, fox and dog (Prince e_t a_1.. 1960; Wolff, 1955). According to Aureli and Kornerup (1949) the Manz glands are present in swine and absent in man. The presence or absence of the Manz gland in various animals has been so controversial y”. “311‘, DJ. 35.55 junctua 12: been tie at TV (Wolff, 19: conjunc'ti._-a The Substa 11 that it was studied by many investigators such as Blumberg (1867), Terson (1893), Zietzschmann (1906) and others in different animals but still the problem is not solved. According to Aureli and Kornerup (1949), Strohmeyer (1859) reported the presence Of the Manz glands in the horse, ox, sheep, pig, roedeer, fox and man. The bulbar con- junctiva lacks goblet cells (Prince gt a_l. . 1960). Sweat glands have been described in the bulbar conjunctiva of the goat, pig, and ox (Wolff, 1955). The substantia propria consists of the superficial adenoid and deep fibrous layers. The superficial layer contains a network of fine connective tissue and lymphocytes. It starts as a thin layer at the subtarsal fold and becomes thick at the fornix (Prince e_t a_1., 1960; Wolff, 1955). At the fornix the propria contains deposits of lymphoid tissue which forms ridge-like prominences separated by grooves. The deep layer of the substantia propria contains thicker fibers and conjunctival blood vessels, nerves and some glands (gland of Krause). The substantia propria contains an abundance of elastic fibers in the horse, dog, ox, and cat. The lymphatic follicles which are absent in man, occur variably in the domestic animals. They are numerous in the ox and known as the "plaques of Brush"; arranged around the cornea in the horse; found more near the medial canthus and in the bulbar conjunctiva in the dog and more developed in the autumn and summer than spring in sheep (Nicolas, 1924). The substantia propria forms a few papillae at the limbus and the lid margin (Prince e_t a__l., 1960; Wolff, 1955). Three kinds of nerve endings: free endings, bulbs of Krause and tufts or ribbons are seen in the conjunctiva (Wolff, 1955). Biochemistry and Histochemistry - According to Krause and Chan (1933) the principal conjunctival chemical constituents are protein (mucin, collagen, elastin, albumin,globulin); lipids (neutral fats, fatty acids, phospholipids and cholesterol); carbohydrates (glucose and lactic acid) and inorganic salts (sodium chloride and phosphates). The conjunctival secretion is slightly acidic, possibly due to calcium urate (Sanyal, 1931). Histochemically the presence of alkaline phosphatase, glycogen and some melanin has been observed in the conjunctiva. Mucin of the conjunctival goblet cells reacts weakly to metachromatic dyes and alcian blue but stains well by H104 and CrO3 Schiff procedures (Lillie, 1954). LACRIMAL CARUNCLE (CARUNCULA LACRIMALIS) G_1mois - The caruncle is a small, oval body generally pigmented in domestic animals (Prince e_t a_1., 1960; Sisson and Grossman, 1953) and flesh coloured in man (Wolff, 1955). It contains a few small hairs. It is developmentally regarded as part of the lower eyelid (Arey, 1954).. Histology - It is covered by stratified squamous epithelium which contains goblet cells in the dog, pig and horse. The dermis contains leucocytes and in the dog, horse and ox, lymph nodules (Trautmann and Fiebiger, 1957). The caruncle also contains modified sweat glands and a few sebaceous glands which open into minute hair follicles. Some seromucous glands (accessory lacrimal glands) are also found in horses and carnivores (Trautmann and Fiebiger, 1957). THE THIRD EYELID (NICTITATING APPARATUS) _G_rqs_s - The third eyelid (palpebra tertia) is a fold Of conjunctiva supported by a cartilage and situated in the inner canthus (Davis, 1929; Trautmann and Fiebiger, 1957). Developmentally it belongs to the conjunctiva (Wolff, 1955). It is absent in fishes except elasmobranchs in which it is represented by an adipose flap (Prince, 1956). It is well developed and very active in the frog and in birds and when stretched it becomes transparent (Stibbe, 1928; Wolff, 1955). In birds and reptiles it contains two special muscles called the pyramidalis and the quadratus which are innervated by the 6th cranial nerve (Wolff, 1955). It is fully developed and active enough to sweep the whole cornea in ungulates but much less developed in carnivora and marsupials (Johnson, 1901), In all primates it becomes vestigeal and is represented by the plica semilunaris (Prince e_t a_1., 1960). The third eyelid of the rabbit has no special muscle but it moves out— ward or inward due to the corresponding contraction or relaxation of the retractor oculi muscle. The levator muscle sends a slip to the base of the third eyelid which might control this movement (Davis, 1929):. The cartilage of the third eyelid is irregularly triangular in shape“ Its wider and thinner part lies in the nictitating membrane; and the narrow, thicker portion medial to the eyeball is surrounded by the nictitating gland (Sisson and Grossman, 1953)° Prince e_t a_lu (1960) described this cartilage as ‘T‘ shaped, The cartilage is absent in birds (Stibbe, 1928; Trautmann and Fiebiger, 1957) and is rarely found in man (Wolff, 1955),, The glands of the third eyelid are classified by Trautmann and Fiebiger (1957) and Prince e_t a_lo (1960) into two groups: the super- ficial (nictitans) and deep (Harderian), The nictitans gland surrounds the cartilage (Trautmann and Fiebiger, 1957) and the Harderian gland is placed at the deep end of the cartilage (Davis, 1929)., (The presence of the Harderian gland was first reported by Harder (1694) in all mammals except some carnivores and primates“ Loewenthal (1892) observed this gland in the mouse, rat, guinea pig, pig, calf, sheep, and horse, According to Giacomini (1887) as cited by Wolff (1955) the Harderian gland is present in all vertebrates, large in mammals, especially in herbivora, rudimentary in the lower apes but absent in v 1 , tile c.1115)” . develope: drazns :nt, the Barrie membram r . . 0: me see the anthropoids, such as man. When the Harderi an gland is well developed, the lacrimal gland is poorly developed and vice versa (Wiedersheim, 1898 cited by Wolff, 1955). It is rudimentary in amphibia and large in serpents and birds (Wolff, 1955) . The Harderian gland of birds is situated at the back of the orbit and drains into the deep internal fornix of the third eyelid. In mammals the Harderian gland is situated in the substance of the ni ctitating membrane, covering the superficial aspect of the inner two-thirds of the deep limb of the cartilage and wrapping around the deep end of the cartilage (Stibbe, 1928) . The Harderian gland is absent in man but present in those animals which have a well developed third i eyelid. The gland of the rabbit is large, complex and surrounded by a delicate capsule and a venous sinus and lies at the base of the third eyelid (Davis, 1929) . Recently Prince e_t aml.(1960) reported its presence in cattle, pigs, and rabbits and its absence in dogs, cats, sheep, and goats. The pig is the only domestic animal which contains the Harderian gland as a separate organ (Trautmann and Fiebiger, 1957) . The Harderian gland of the ox is confluent with the nictitating gland and both are surrounded by a common sheath (Prince et 51.1" 1960) . Histology - The conjunctiva of the third eyelid of domestic animals contains scattered lymphocytes and lymph nodules (Prince e_t 31., 1960; Trautmann and Fiebiger, 1957) and many goblet cells in man (Wolff, 1955). The free margin of the third eyelid contains pigment cells and elastic tissue in domestic animals and man (Prince e_t 31., 1960; Wolff, 1955). The presence of smooth muscle in the third eyelid of vertebrates was denied by Ihle (it a_1. (1927) but was observed by Lawrentjew and Borowskaja (1936), Groyer (1903) and Stibbe (1928) in various mammals. Acheson (1938) observed two sheets of well developed smooth muscle in the nictitating membrane of cats. The base of the human plica semilunaris contains some smooth muscle fibers and fat (Wolff, 1955). The cartilage of the third eyelid is generally hyaline in domestic animals except in the horse, cat and pig in which it is elastic. It is lacking in birds (Trautmann and Fiebiger, 1957). The cartilage is incased by collagenous tissue which sends septa into the surrounding nictitans gland (Price e_t 3L1“ 1960). The superficial gland of the third eyelid (nictitating gland) which surrounds the cartilage is serous in the horse and cat, mixed in the ox, sheep and dog and mucous in the pig (Trautmann and Fiebiger, 1957). Histologic structure of the nictitating gland of domestic 1 animals resembles the lacrimal gland. The gland is covered by a connective tissue sheath which invades the parenchyma by many septa containing ducts, blood vessels, nerves and in some animals fat cells. The acini are lined by a single layer of pyramidal cells and the ducts by one or two layers of columnar cells (Prince e_t a_l., 1960). The nictitans gland of the rabbit has several ducts which pierce the cartilage and open on the inner surface of the membrane. The gland is made up of small acini, the cells of which contain numerous secretion grandules (Davis, 1929). The histology of the Harderian gland was first described by Loewenthal (1892) in the guinea pig, mouse, rat, pig, sheep, calf and horse. The microscopic structure of the gland has been studied in pigs, horses and mules by Aureli (1957) and Aureli and Tanzii (1959); in rabbits by Bjo'rkman e_t a_l. (1960), Davis (1929) and Schnier (1950); in rats and mice by Chiquoine (1958), in birds and domestic animals by Stibbe (1928), and in mammals by Wendt (1877 cited by Wolff, 1955). According to these authors the Harderian gland is a tubuloalveolar gland. Harderian glands sometimes have two lobes, one white, the other pink which differ in histologic structure. Large fat globules are I”; C .1 11. D: p seen in the pink lobe whereas only small fat droplets are present in the white lobe. The ducts open on the bulbar surface of the nictitat- ing membrane. The structure of the Harderian gland is sometimes reminiscent of a sebaceous gland and holocrine in nature (Aureli and Carelli, 1956). According to Cohn (1955), Davis (1929) and Paule (1958) it is an apocrine gland. Myoepithelial cells are also found in this gland (Chiquoine, 1958). Histochemistry - On histochemical examination, Aureli and Tanzii (1959) reported that the glands of the third eyelid of the horse and mule contain mycopolysaccharides, lipids, nucleic acid and enzymes. They considered the gland seromucous in type. Materazzi and Travaglini (1961), from their research on the orbital glands of the various mammals, reported that the secretion of the third eyelid of sheep contains a PAS positive substance. Histochemical studies of the Harderian gland were done in the pig by Aureli (1957); in mice and rats by Cohn (1955), Collins (1957) and Grafflin (1942); in rodents by Derrien and Turchini (1924); in amphibia, reptiles and birds by Paule (1958); and in rabbits by Schneir (1950). According to these authors and Prince e} a_l. (1960) five types of Harderian glands have been recognized in the vertebrates, four of which occur in mammals: lipid secreting, mucous, seromucoid and mixed. Most mammals have lipid secreting Harderian glands. The presence of phospholipids, triglycerides, cholesterol, alkaline and acid phosphatases, lipase, proteins, iron and glycogen in the Harderian gland have been observed in the albino mouse by Cohn (1955) and in rabbits by Schneir (1950). The yellow-brown pigment (porphyrin) was observed in the Harderian glands of mice by Collins (1957) and of rabbits by Schneir (1950). PERIOR BITA (ORBITAL PERIOSTEUM) The periorbita or orbital periosteum lines the bony wall of the orbit (Wolff, 1955). It is a conical fibrous membrane which encloses 17 the eyeball and its associated structures (Sisson and Grossman, 1953) with the exception of the lacrimal gland which lies outside the cone in a special compartment formed by the periorbita (Prince e_t a__l. , 1960). The apex of the periorbita is attached at the orbital group of foramina and its base is attached to the orbital margin and continued as the fibrous layers of the lid. It is thin medially where it comes in contact with the bony wall of the orbit and thick laterally where it is reinforced by the elastic fibers which are attached to the pterygoid crest (Sisson and Grossman, 1953). It consists of two layers: outer, containing loose collagenous and fine elastic fibers and spindle shaped connective tissue cells, and inner, containing dense connective tissue and blood vessels (Prince _e_t a_l., 1960). ORBITAL FASCIA The bulbar fascia (Tenon's capsule) is a thin fibrous membrane which covers the eyeball from the corneo-scleral junction to the optic nerve (Wolff, 1955) and separates the eyeball from the orbital fat (Bedrossian, 1958). Its inner surface is attached to the sclera by fine trabeculae and the outer surface is in contact with the orbital fat. Tenon‘s capsule is pierced anteriorly by the tendons of the extrinsic ocular muscles and posteriorly by the Optic nerve and ciliary arteries and nerves. The lower part of Tenon' 3 capsule which is thickened to form a sling or hammock for the eyball is known as the ligament of Lockwood (Wolff, 1955). This ligament is attached laterally and medially to the wall of the orbit by condensed fibrous tissue called the check ligaments. Muscular fasciae (muscle sheaths) are reflections of Tenon's capsule over the ocular muscles. These muscle sheaths also extend from one muscle to others forming the intermuscular membrane (Bedrossian, 1958). 18 EXT RINSIC OCULAR MUSC LES A historical survey of extrinsic ocular muscle was made by Cole (1944). According to him eye muscles including the retractor oculi (choanoid) and the cutaneous muscles of the eyelids were care- fully explored by Galen. Vesalius found the retractor oculi muscle originally in the dog but described it in man as he was not aware that it is absent in man and higher mammals. Casserius was the first to demonstrate that the retractor oculi muscle does not occur in man. This muscle reaches its highest development in some ruminants where it forms a continuous cone surrounding the optic nerve as it enters the orbit. The retractor oculi has received a variety of names such as posterior rectus, suspensor colli and choanoid. Gross - The orbital muscles are poorly developed in invertebrates but well developed in vertebrates. In fishes, amphibia, reptiles, and birds these muscles are less mobile (Wolff, 1955). The gross anatomy of the ocular muscles has been described in every text book of anatomy both animal and man. According to Prince e_t a_1_1.(1960) and Sis son and Grossman (1953), extrinsic ocular muscles in domestic animals are four recti, two oblique and one retractor. In the rabbit, Davis (1929) described ten extrinsic ocular muscles namely the orbicularis, levator palpebrae superioris, depressor palpebrae inferioris, four recti, two oblique and retractor bulbi. In addition to six extrinsic skeletal muscles in the human orbit, Wolff (1955) described four groups of smooth (capsulo-palpebral) muscles namely, the superior, inferior, superolateral and superomedial palpebral. The retractor oculi is absent in birds and serpents (Wolff, 1955). The branches of the external ophthalmic and malaris arteries supply blood to these muscles (Prince and Ruskell, 1960). These muscles are innervated as follows: the superior, inferior and medial recti and inferior oblique by the oculomotor, the lateral rectus and retractor oculi 19 by the abducent and the superior oblique by the trochlear (Sisson and Grossman, 1953). Histology - As these extrinsic skeletal ocular muscles are derived from the branchial arches, they are more highly differen- tiated than other skeletal muscles of the body (Wolff, 1955). Since these muscles have the smallest fibers of all voluntary muscles and their striations are poorly developed, they appear intermediate between skeletal and smooth muscles (Bedrossian, 1958). Many nerve and elastic fibers are seen between the muscle bundles. In the past, there was a controversy about the existence of sensory muscle spindles in these muscles but through recent investigations it is now well established that they exist in man as well as in animals. Daniel (1946) and Cooper and Daniel (1949) reported muscle spindles in the human extrinsic muscles of the eye. According to Prince e_t a_l. (1960), Wolter (1954) observed six different types of sensory nerve endings in the human extrinsic ocular muscles. Fukuda (1958) found five distinct kinds of nerve endings in the extrinsic ocular muscles of the rabbit and traced them to the oculomotor nerve and cervical sympathetic ganglion. According to him, the muscle spindles were absent, but definite sensory nerve endings of thin medullated nerve fibers were present. In these muscles of dogs according to Fukuda (1958), Kure, Shiba and Okinaka (1931) described four types of nerve endings derived from pyramidal (motor), extrapyramidal, sympathetic and parasympathetic nerves. Sensory nerves were not reported by them. The existence of the muscle spindles in the extrinsic ocular muscles of sheep and goats was confirmed by Cilimbaris (1910). Winckler (1936, 1937) reported the presence of proprioceptive nerves in these muscles of sheep and goats. Whitteridge (1955) found a separate afferent nerve supply to these muscles in goats. 20 THE LACRIMAL APPARATUS Lac r imal Gland m - The lacrimal gland is a modified cutaneous gland developed from the conjunctival sac (Wolff, 1955). Fishes have no lacrimal gland. The change of the environment from aquatic to terrestrial, necessitated the development of a secretory apparatus in connection with the eyes. Thus in the urodeles, a series of glands develop from the conjunctiva of the lower lid. In anurans and reptiles they become more developed and divided into the lateral and medial groups, the lateral being the lacrimal, and the medial the Harderian glands. In mammals, the process of evolutiOn continues until the gland comes to lie beneath the upper lid (Kingsley, 1917; Prince 1956). The development of the lacrimal gland of the rabbit, guinea pig, pig, sheep and man was studied by Falchi (1905). Gross anatomy of the gland was described by Ellenberger and Baum (1943). Prince e_t a_l. (1960) and Sisson and Grossman (1953) in various domestic animals. The gland is situated at the lateral angle in birds, slightly in the upper but mostly in the lower lid in rabbits (Davis, 1929; Wolff, 1955) below the supraorbital process in the horse and beneath the orbital ligament in the dog (Smythe, 1956). The gland of the ox is better developed and is divided into two lobes, the upper and lower (Sisson and Grossman, 1953). The gland is innervated by the lacrimal, sympathetic and parasympathetic nerves. Parasympathetic fibers in cats reach the gland through the lacrimal nerve (Botelho, 1964). The gland of the ox is supplied by the lacrimal artery which is a branch of the ophthalmic artery (Sundwall, 1916). Histology - The lacrimal gland is a tubuloalveolar serous gland in the cat, horse, ox, pig, and rabbit, mixed in dogs and sheep and compound tubuloalveolar mucous in the goat (Prince e_t a_._1., 1960). 21 The goat‘s lacrimal gland is described by Trautmann and Fiebiger (1957) as a mixed tubuloalveolar gland. Various other authors such as Prince e_t all. (1960), Wolff (1955) and according to Sundwall (1916), B011 (1868), Ellenberger and Gunther (1888), Flemming (1888), and Leydig (1857) have described the microscopic structures of the lacrimal gland in the domestic animals and man. In the lacrimal gland of the ox numerous plasma cells are noted in both the inter- lobular and intralobular tissue, especially around the ducts and between the acini (Sundwall, 1916). The presence of plasma cells has been reported in the human lacrimal gland by Hannes (1911). The blood supply and lymphatics of the gland have been studied by Prince and Ruskell (1963) and Puglisi-Allegra (1904) in the domestic animals. Dogiel (1893) using methylene-blue and Golgi‘s methods observed a peritubular and intercellular network of nerve fibers in the lacrimal gland of the guinea pig and rabbit. Puglisi-Allegra (1903) used Golgi's method and vital staining with methylene blue and observed peritubular, pericellular and intracellular fibers, and sympathetic ganglia cells situated along the course of the sympathetic fibers in the lacrimal gland of the pig. Hisada and Botelho (1963) studied the functional innervation of the lac rimal gland in the cat. Kato (1958) found medul- lated and non-medullated nerve fibers and nerve endings in the human lacrimal gland. Biochemistry and histochemistry - In all domestic mammals the secretory cells of the lacrimal gland contain fat droplets (Trautmann and Fiebiger, 1957). A histochemical study of the lacrimal gland in dogs and cats was done by Materazzi and Travaglini (1961). By histo- chemical methods Spicer and Duvence (1964) observed mucopoly- saccharides in the exorbital lacrimal glands of the hamster, mouse and rat and reported the abundant presence of ribonucleic acids in the lacrimal gland of the hamster. According to Krause (1934) Seki (1926) 22 noted cholesterol in the tears of rabbits. According tO Fleming and Allison (1925) the protein in the tears Of the horse, cow, sheep, turkey and man is species specific. Goldsworthy and Florey (1930) reported that the tears Of dogs and goats possess bacteriolytic properties. Fleming and Allison (1922) discovered a bacteriolytic substance (lysozyme) inthe tears and tissues Of all animals. Lac rimal Excretory Ducts Gross - The number Of excretory ducts are 12 to 16 in the horse, 6 to 8 large and several small ones in the ox and 4 tO 5 in the pig (Prince 631: 3-1., 1960; Sisson and Grossman, 1953). The ducts in dogs are tOO small to distinguish grossly but Open into the superior fornix. In the horse they Open on the conjunctival surface Of the upper lid near the lateral canthus (Smythe, 1956). In cattle the ducts are well deve10ped and Open in a line on the lateral half of the superior palpebral conjunctiva about 1. 5 cm behind the lid margin (Sundwall, 1916). These ducts in the camel Open together in a wide tunnel-like recess in a conjunctival fold just above the posterior (lateral) canthus (Tayeb, 1962). The excretory ducts in primates mostly Open in the upper lid but some always Open in the lower one also. In the tortoise, bird, rodent, and lamb, these ducts unite to form a single duct which Opens in the lower lid (Wolff, 1955). Histology - In domestic animals the smaller excretory ducts are lined with a single layer Of cuboidal cells; the larger ones have two layers. In the pig the epithelium becomes high columnar (Trautmann and Fiebiger, 1957). In sheep the intertubular ducts are lined by a single layer of cuboidal cells surrounded by a heavy, coarse con— nective tissue sheath (Prince e} a_l. , 1960). The excretory ducts Of cattle are lined with stratified cuboidal epithelium containing many goblet cells (Sundwall, 1916). 23 Puncta lac rimalia In domestic animals the Puncta lacrimalia, the entrances of the canaliculi, are generally two in number, situated one on each lid margin near the medial canthus. The lower one is sometimes absent in the dog and always absent in the pig. The rabbit has only one punctum situated on the inner surface of the lower lid (Prince e_t a_l. , 1960). Each punctum lacrimale of the camel is protected by two papillae, one in front and the other behind (Tayeb, 1962). In birds, both puncta enter a wide lac rimal canal which Opens into the nasal cavity immediately above the inner nares (Nicolas, 1924). The open- ing is lined by the continuation Of the conjunctiva Of the lid margin and is surrounded by collagenous tissue and a few fibers from the orbicu- laris oculi muscle (Wolff, 1955). Lac rimal Canaliculi The canaliculi (lacrimal ducts) in domestic animals are two, one in each lid, except there is only one lacrimal duct in the pig and ewe (Wolff, 1955), the rabbit and bat (Minamikawa, 1958) and some- times the dog (Prince e_t a_._1. , 1960). The ducts are entirely absent in the seal, hippopotamus and elephant (Wolff, 1955). The wall Of the upper canaliculus Of swine contains cartilage (Trautmann and Fiebiger, 1957). The ducts are lined by stratified squamous epithelium (Minamikawa, 1958). Lacrimal Sac The lacrimal sac, the dilated origin of the nasolacrimal duct is situated in the lac rimal fossa which is the funnel like orbital end Of the osseous lacrimal canal (Sisson and Grossman, 1953). The sac receives its blood supply through the branch Of the malaris artery (Prince and Ruskell, 1960). In man, the sac is innervated by the 24 infra-trochlear and anterior superior alveolar nerve (Wolff, 1955). The sac Of domestic animals is lined by stratified epithelium which may be columnar or transitional in the pig. The tunica propria in the horse contains lymphocytes and sometimes lymph nodules (Trautmann and Fiebiger, 1957). Nasolac rimal Duct The nasolacrimal duct originates from the lacrimal sac, passes anteriorly first through an osseous canal, then in an osseous groove and finally Opens near the nostril on the lateral wall of the nasal cavity in the ox, on the skin Of the floor of the nostril in the horse and on the lateral wall of the nostril in the dog (Sisson and Grossman, 1953). The nasolacrimal canal is curved, 25-30 cm long and 4-5 mm wide in the horse, short and almost straight in the ox and pig. There is no valve near the lacrimal sac in the domestic animals as seen in man. Sometimes its nasal opening is represented by two or several openings in the horse (Nicolas, 1924). The nasolacrimal duct usually opens into the nasal cavity, but in some burrowing snakes it Opens into the mouth which suggests that tears developed not only to moisten the eye but also to moisten the nose and mouth. In lizards and in most snakes the duct Opens into the organ of Jacobson (Botelho, 1964). Minamikawa (1958), after studying the comparative anatomy of the ductus nasolacrimalis in the rabbit, dog, cat, mouse, guinea pig, bat and mole reported that the duct was lined with stratified squamous epithelium and was surrounded by a venous plexus. He also Observed the absence of smooth muscle in the wall Of the duct. According to Trautmann and Fiebiger (1957) the duct of the horse contains mucous glands and lymph nodules in the subepithelial layer. MATERIALS AND METHODS Sourc e Of Animals The animals used for this investigation were obtained from the Dairy, Physiology (endocrine research unit) and Surgery and Medicine Departments at Michigan State University. All animals except one were slaughtered for meat purposes and were clinically healthy. One animal which was used for urethrotomy was electrocuted in the postmortem room. Specimens were collected within 10 to 20 minutes after slaughter. For histologic study, the eye specimens were ob- tained from 15 different areas Of the eye adnexa of 8 male sheep, 2 weeks to 5 months old; 8 female sheep, 3 months to 4 years old and 4 male goats, 5 days to 5 months old. In addition, 4 heads of female sheep 3 to 4 years old were used for gross anatomy. For histochemical study, frozen specimens from 2 sheep, 2 months and 2 years Old and 2 goats, 5 days old were used. Paraffin processed specimens from all animals were used for histologic study. Technique For gross anatomy 10% formalin fixed and latex injected speci- mens were dissected. For the study Of the course of the lacrimal drainage passage and blood vessels Of the orbit a radiopaque substance (”Micropaque”*) was mixed with water and injected into them and radiographs Were taken. For the detailed study of the blood vessels Of the eyelids, muscles and lacrimal glands, India ink was injected into the carotid artery. The eyelids, lacrimal glands and extrinsic ocular =I PLATE V Blood supply to the eye of sheep Radiograph (reduced) (1) Internal maxillary artery, (2) Malar artery, (3) Superficial temporal artery, (4) Lacrimal artery, (5) Bony orbit, (6) Eyeball, (7) External ophthalmic artery, (8) Frontal vein 60 (b) PLATE VI (a) Blood supply to the eyelids and eye muscles of sheep Radiograph (reduced) (1) Superior medial palpebral artery, (2) Inferior medial palpebral artery, (3) Superior lateral palpebral artery, (4) Lateral commissural artery, (5) External ophthalmic artery and muscles (b) Lacrimal passage of sheep Radiograph (reduced) (6) Lacrimal canaliculi, (7) Lacrimal sac, (8) Nasolacrimal duct, (9) Hard palate 61 PLATE VII Blood supply to the eyelids of sheep India ink injected, 7X (1) Branch from superior lateral palpebral artery, (2) Palpebral fissure, (3) Inferior medial palpebral artery, (4) Blood sinus of sensory hair of lower eyelid 62 PLATE VIII Blood supply to the lacrimal gland of sheep India ink injected, 11X (1) Lobular lacrimal artery, (2) Interalveolar artery, (3) Intra' alveolar artery, (4) Alveolus 63 PLATE IX Skeletal muscle fibers inserting into the skin of the eyebrow of the sheep Vertical section,H. and E. Stain, 236X. (l) Stratified squamous epithelium, (2) Frontalis muscle fibers, (3) Sebaceous gland, (4) W001 hair, (5) Sweat gland, (6) Bulb of the supercilium 64 anew! PLATE X Eyebrow of the goat Vertical section,l-l. and E. Stain, 48X (1) Stratified squamous epithelium, (2) Sinus hair, (3) Coat hair, (4) Supercilium, (5) Dermis 'ii’v'f'lt I ‘ PLATE XI Tarsal glands of the upper eyelid of sheep Frontal section,I-I. and E. Stain, 53X (1) Marginal palpebral conjunctiva with rete pegs, (2) Tarsal glands, (3) Central duct lined with stratified squamous epithelium 66 ii I a ‘5” Laser PLATE XII Skeletal muscle arrangement in the upper eyelid of the goat Oblique section,H. and E. Stain, 63X (1) Stratified squamous epithelium, (2) Coat hair, (3) Sinus hair, (4) Levator palpebrae superioris muscle fibers, (5) Frontalis muscle fibers, (6) Orbicularis oculi muscle fibers PLATE XIII Ciliary follicle of the lower eyelid of sheep Vertical section,,A1cian Blue Stain, 240x (1) Sebaceous gland,*(2) Follicular folds, (3) Thickened epithelium, (4) Nerve plexus; (5) Root of cilia, (6) Gland of Moll * Commonly termed gland of Zeis 68 ~ . .’ a ‘c. ~33 t'a-w‘y. w‘w‘ . '4” w fa? car-'5'” ‘/ n V“ 4'- ., M a ‘ If. 1 . ‘v , N. PLATE XIV LOWer eyelid of sheep Vertical section,H. and E.Stain. 54X (1) Lymph nodule, (2) Muscle of Miiller, (3) Fat cells, (4) Fornix conjunctiva \ PLATE XV Glands of Moll in the lower eyelid of sheep Cross section, PAS reagent, 440X (1) Cuboidal epithelium, (2) Myoepitheliurn, (3) PAS positive basement membrane, (4) Fibroblast, (5) Muscles of Riolan PLATE XVI Muscles of Miiller ending in elastic fibers in the lower eyelid of sheep Vertical section,Weigert and Van Gieson's Stain, 225X (1) Muscle of Miiller, (2) Elastic fibers, (3) Substantia propria, (4) Lymph nodule near palpebral conjunctiva 71 PLATE XVII Tactile hair of the lower eyelid of sheep Transverse section at the level of sebaceous gland, Mallory's triple stain, 222x (1) Tactile (sensory, sinus) hair, (2) Epithelial sheath, (3) Intra- epithelial terminal sebaceous lobule, (4) Fibro-elastic trabeculae, (5) Multilobulated sebaceous glands, (6) Outer connective tissue sheath .72 PLATE XVIII Lacrimal (infraorbital) pouch glands of sheep Vertical section,H. and E. Stain, 50X (1) Stratified squamous epithelium, (2) Hair follicle, (3) Lacrimal pouch gland (modified multilobulated sebaceous gland), (4) Sweat gland, (5) Hair bulb PLATE XIX Upper palpebral marginal conjunctiva of sheep Vertical section,H. and E. Stain, 324x (1) Degenerating cells of tarsal, (Meibomian) gland near the central duct lined by stratified squamous epithelium, (2) Tarsal gland capsule and substantia propria fused, (3) Stratified squamous marginal conjunctival epithelium with rete pegs, (4) Muco-cutaneous junction showing keratinized and nonkeratinized epithelium 74 PLATE XX Upper palpebral tarsal conjunctiva of sheep Vertical section,H. and E. Stain, 277X (1) Tarsal gland, (2) Tarsal capsule and substantia propria fused, (3) Stratified squamous epithelium, (4) Conjunctival epithelial rete peg 75 PLATE XXI Upper palpebral tarsal conjunctiva of the goat Vertical section,H. and E. Stain, 266x (1) Tarsal conjunctiva, (2) Epithelial "buds, " (3) Substantia propria, (4) Artery, (5) Tarsal (Meibomian) gland PLATE XXII Upper palpebral post-tarsal conjunctiva and lacrimal excretory duct of sheep Vertical section,H. and E. Stain, 267X (l) Lacrimal excretory duct, (2) Stratified columnar epithelium, (3) Goblet cells, (4) Substantia propria, (5) Stratified cuboidal conjunctival epithelium, (6) Lymph nodule 77 PLATE XXIII Fornix conjunctiva of sheep Vertical section,A1cian Blue Stain, 608X (l) Stratified cuboidal epithelium, (2) Goblet cells, (3) Substantia propria containing lymphocytes, (4) Fornix ' 78 PLATE XXIV Fornix and lower palpebral post-tarsal conjunctivae of sheep Vertical section,H.. and E. Stain, 49X (1) Stratified cuboidal post-tarsal conjunctival epithelium, (2) Substantia pr0pria, (3) Lymph nodules, (4) Fornix, (5) Conjunctival fold, (6) Bulbar conjunctiva 79 .\ A.._\I I\ 1.... 5.1...» 1 .\ . II. PLATE XXV Reticular fibers in the fornix and lower palpebral post—tarsal conjunctivae of sheep 214x 3 reticular stain Gomori' (1) Post-tarsal conjunctiva, (2) Fornix conjunctiva, (3) Bulbar conjunctiva, (4) Goblet cells, (5) Reticular fibers, (6) Lymph nodule with reticular fibers 9 Vertical section 80 PLATE XXVI Limbal conjunctiva of sheep Vertical section,H. and E. Stain, 203X (1) Limbal conjunctiva, (2) Conjunctival epithelial rete pegs, (3) Corneal epithelium, (4) Sclera, (5) Connective tissue pig- ment cells 81 PLATE XXVII Bulbar and limbal conjunctivae of the goat Vertical section,H. and E. Stain, 257x (1) Bulbar conjunctiva, (2) Conjunctival fold, (3) Limbal conjunctival epithelial thickening (4) Vein, (5) Sclera 82 PLATE XXVIII Lacrimal caruncle of sheep Longitudinal sectioniPAS reagent, 44X (1) Upper eyelid, (2) Stratified squamous epithelium (caruncular conjunctiva), (3) Hair, (4) Sebaceous gland, (5) Sweat gland, (6) Membrana nictitans, (7) Goblet cells 83 lemu‘ ... a) ..\. . PLATE XXIX Membrana nictitans of sheep Longitudinal section,H. and E. Stain, 68X (1) Stratified squamous conjunctival epithelium with rete pegs, (2) Fold on outer surface, (3) Nictitans hyaline cartilage covered with perichondrium 84 PLATE XXX Membrana nictitans of the goat Longitudinal section,H. and E. Stain, 49X (1) Stratified squamous epithelium with rete pegs, (2) Fold on outer surface, (3) Nictitans hyaline cartilage covered with perichondrium, (4) Groove on ventral surface 85 PLATE XXXI Nictitans gland and fornix conjunctiva of sheep Vertical section,H. and E. Stain, 68X (1) Nictitans conjunctival fold, (2) Lymph nodules, (3) Nictitans gland, (4) Nictitans hyaline cartilage, (5) Nictitans excretory duct lined with stratified columnar epithelium containing many goblet cells, (6) Deep nictitans fornix, (7) Conjunctival folds, (8) Limbal conjunctival rete pegs, (9) Sclera, (10) Bulbar conjunctival fold PLATE XXXII Nictitans gland of sheep Longitudinal section,A1cian Blue Stain, 49X (1) Superficial fornix, (2) Nictitans hyaline cartilage, (3) Peri- chondrium, (4) Mucous alveoli, (5) Serous alveoli, (6) Interlobular duct, (7) Trabeculae, (8) Deep fornix 87 PLATE XXXIII Nictitans gland with excretory duct of sheep Longitudinal section,H. and E. Stain, 74X (1) Serous alveoli, (2) Mucous alveoli, (3) Interlobular fat, (4) Excretory duct lined with stratified columnar epithelium con- taining many goblet cells, (5) Deep nictitans fornix 88 PLATE XXXIV Nictitans gland of sheep Vertical section,PAS reagent, 236x (1) Mucous alveoli, (2) Serous alveoli, (3) Duct with PAS positive luminal content, (4) Interlobular fat cells in trabecula, (5) Plasma cells 89 “93¢“; .3 "l- ' '- 'V .,-| h, 'J. PLATE XXXV Nictitans gland with excretory duct of the goat Longitudinal section,H. and E. Stain, 57X (1) Deep nictitans fornix, (2) Lymph nodule, (3) Excretory duct, (4) Nictitans gland, (5) Nictitans hyaline cartilage covered by perichondrium PLATE XXXVI Nictitans gland of the goat Vertical section,PAS reagent, 720X (1) Seromucous mixed alveolus, (2) interalveolar tube, (3) PAS positive alveolus, (4) Alveolar duct, (5) Interalveolar plasma cells 91 PLATE XXXVII Periorbita and orbital septum of sheep Vertical section,Weigert and Van Gieson's Stain, 46X (1) Lacrimal sac, (2) Periorbita (orbital periosteum), (3) Arcus marginale, (4) Periosteum, (5) Orbital septum, (6) Orbicularis oculi, (7) Bony orbital margin 92 56": -" s" t 1'“ PLATE XXXVIII Bulbar fascia (Tenon's capsule) of sheep Vertical section,H. and E. Stain, 250x (1) Extlinsic ocular muscle,- (2) Muscular fascia, (3) Orbital fat, (4) Bulbar fascia, (5) Sclera 93 PLATE XXXIX Lacrimal gland and smooth muscle of sheep Vertical section, H. :ind E. Stain, 295x (1) Lacrimal gland, (2) Loose areolar tissue (capsule), (3) Smooth muscle, (4) Muscular sheath , PLATE XL , Lacrimal gland of sheep Cross section,Alcian Blue Stain, 275X (1) Mucous (Alcian blue positive) alveoli, (2) Serous alveoli, (3) Interlobular duct lined with stratified cuboidal epithelium, (4) Goblet cells, (5) Trabeculae 95 PLATE XLI Lacrimal gland of sheep Vertical section,PAS reagent, 684X (l) Trabecula, (2) Mucous (PAS positive) alveoli, (3) Serous alveoli, (4) Mixed (seromucous) alveoli, (5) Interalveolar duct, (6) Interalveolar plasma cells 96 PLATE XLII Lacrimal gland of the goat Vertical section, PAS reagent, 646X (l) Mucous (PAS positive) alveoli, (2) Seromucous (mixed) alveoli, (3) PAS negative duct epithelium, (4) Plasma cells, (5) Vein 97 PLATE XLIII Lacrimal gland of the goat Vertical section,H. and E. .Stain, 1704X (1) Alveolar lumen, (2) Pyramidal glandular cell, (3) Spherical nucleus, (4) Plasma cells 98 PLATE XLIV Lacrimal excretory duct origin in sheep Vertical section,H. and E. Stain, 48X (1) Capsule, (2) Trabeculae, (3) Smooth muscle fibers, (4) Lobules, (5) Intralobular duct, (6) Lobular duct, (7) Interlobular duct, (8) Excretory duct N to PLAT E XLV Lacrimal excretory duct of sheep Transverse section,PAS reagent, 394X (1) Goblet cells (PAS positive), (2) Apical projection of goblet cells, (3) Stratified columnar epithelium, (4) PAS positive luminal content, (5) Substantia propria 100 '\. x». n3 .. a‘ m \ “cL‘ ‘n r “it .,; ags 2‘ ~'~'-‘ 2 (hi-'91” “w- -..v, i - v “ \ “ v i ‘39.: i“ , 5. “Sr. , V 1" 5R ~'Jn‘5.\$iku}i: K\:_ \ v ’i V -. a ' ’13 1.1;, V'. r’ V . «sit. i2":- _. “fr;‘n4 V} 9"};- 9% f r.‘ '. g: ‘ifi‘x‘l‘fiii‘iz 3i 23: 4,“; ‘7! .s‘wé‘m ~' ..‘ .':‘- c N r ' t \01' (‘5 V 3‘4?!“ 1’ 2“"! \‘rMJIL‘. . we»: . , ‘c‘ w i‘» 45.3%. A" M ‘ 2" 1‘ 31‘3““. 9"?{95‘ [’Ir 1 /d‘\ " ‘ga f:"- ' F,‘lan .’ I 0‘, ' 3w; $.9e3.'féf.s~: I ”5.5‘19' ‘ ‘J' *\ -:.‘\- .{o- \ _ s PLATE XLVI Lacrimal excretory duct of sheep Vertical section,H. and E. Stain, 51X (1) Upper eyelid, (2) Smooth muscle bundle, (3) Tarsal gland, (4) Excretory duct, (5) Lymph nodule, (6) Post-tarsalconjunctiva 101 ’1 ,4 . i2 “K 2 9’, I -' ' fl \ ' x. ‘1. . heat»: 1 ' '\.I 1 '9 ,, 3.: ., ,2. ,1 . "a. j 'if,“ f, 4’ 5‘ in 3 s '42 \v to em- .0 *4? s 1f: ‘ "“4 if \ v9 ‘ - , . \ ‘1" A‘w .. ‘1 )\ f. "‘\\. ‘ last/«(f . PLATE XLVII Lacrimal excretory duct of the goat Cross section,H. and E. Stain, 525X (1) Luminal content, (2) Stratified cuboidal epithelium, (3) Goblet cell, (4) Substantia propria PLATE XLVIII Lacrimal canaliculi of sheep Vertical section,H. and E. Stain, 278x (1) Stratified squamous epithelium, (Z) Substantia propria, (3) Vein I 103 PLATE XLIX Lacrimal sac of sheep Vertical section,H. and E. Stain, 600x (1) Stratified columnar epithelium, (2) Columnar cell extending ' towards base, (3) Connectivetissue pigment cells, (4) Substantia propria 104 PLATE L Lacrimal sac of sheep Vertical section,H. and E. Stain, 1065X (1) Stratified columnar epithelium, (2) Columnar cell extending towards base, (3) Capillaries, (4) Substantia propria, (5) Venous Sinus 105 PLATE LI Lacrimal sac of sheep Vertical section, Alcian Blue Stain, 630X ' (1) Stratified cuboidal epithelium, (2) Goblet cell, (3) Capillaries, (4) Venous sinus, (5) Substantia propria, (6) Developing goblet cells 106 PLATE LII Lacrimal sac and nasolacrimal duct of sheep Vertical section,H. and E. Stain, 300X (1) Lacrimal sac, (2)N.asolacrima1 duct, (3) Stratified columnar epithelium, (4) Substantia propria, (5) Venous sinus 107 PLATE LIII Nasolacrimal duct and lacrimal pouch gland of sheep Vertical section,Mallory's triple stain, 220x (1) Lacrimal pouch (modified sebaceous) gland, (2) Duct of pouch gland, (3) Sweat gland, (4) Periosteum, (5) Bone, (6) Venous plexus, (7) Nasolacrimal duct lined with stratified columnar epithelium, (8) Nasal epithelium, (9) Pouch epithelium 108 wvlmi- . Mfg fi/ j. o ...\s 1\ Ag...n/;.f\ .\:...aw..\.-n .. .M/sv .«a J. ”3.1. .fiwlv/g - . . , 11.15.71 . . :13; \uii. 5.).» 1 . ,fliao...\. as“. so“ 9 x 1. s .vn‘ 0. 1w) Ifm‘ \ 1‘ u \ v .. nu \s. ’. \\ I w. l. J ’ \‘Rnl .. 1:15». . . 3. x u x . a. ‘.\.... .sY \ A... PLATE LIV (l) Weakly PAS positive stratified columnar epithelium Nasolacrimal duct of sheep: midportion (2) Substantia propria, (3) Venous plexus Cross section,PAS reagent, 78X 109 PLATE LV Nasolacrimal duct of sheep: midportion Vertical section,H. and E. Stain, 303x (1) Nasal epithelium, (2) Goblet cells, (3) Nasolacrimal duct lined with stratified columnar epithelium, (4) Venous Sinus, (5) Seromucous gland 110 PLATE LVI Nasolacrimal duct of sheep: Distal portion Longitudinal section, Alcian Blue Stain, 198x (1) Stratified cuboidal epithelium, (2) Goblet cells, (3) Intra- epithelial vacuoles, (4) Lumen of the duct, (5) Venous sinus lll c. . p I‘.‘|I": leiz.‘ {a ' Jr" \. ' "if. ’ "l" *‘ ‘ 0 a 7” O “ ' l. 30‘ ".. . ‘u .‘ l‘ . W. 'l 0' n :I' A ' s H t 1’?!“ - . ‘ ‘1". I] ” ‘ “ "I‘ Q - Ma. (- 4.»; l o- o - 'll :2 54¢? 9’ ’u .‘D d \ .2 .g’. 783' "O. PLATE LVII The nasolac rimal duct of the goat: proximal portion Vertical section,H. and E. Stain, Z40X (l) Nasolacrimal duct lined with: stratified columnar epithelium (l) Stratified columnar epithelium, (2) Single goblet cells, (3) Group of goblet cells, (4) Venous sinus, (5) Substantia propria 112. m 1' '0‘). “I" 5 g. .1 .' .. ', a.) . 13', ._‘ PLATE LV III Nasolacrimal duct of the goat: midportion Cross section,H. and E. Stain, 76X (1) Stratified columnar epithelium of nasolacrimal duct, (2) Venous plexus in substantia propria, (3) Seromucous gland, (4) Pseudo- stratified columnar nasal epithelium S UMMARY AND CO NC LUSIONS To investigate the gross anatomy, histology and histochemistry of the eye adnexa, specimens from 20 sheep, 2 weeks to 4 years old and 4 goats, 5 days to 5 months of age, were used. The following conclusions are drawn: Eyebrows are represented by numerous sensory and a few superciliary hairs° The medial palpebral commissure of sheep is unpigmented and grooved leading to a lacrimal pouch which contains large multilobulated sebaceous glands. Goats lack the lacrimal pouch. Smooth tarsal muscle (muscles of Muller) and marginal palpebral skeletal muscles (muscles of Riolan) are well developed. The conjunctival epithelium is very irregular being stratified squamous to cuboidal to columnar and even transitional at a few places. It contains many goblet cells and a varying number of lymphocytes. Lymph nodules are more numerous in sheep. The post— tarsal conjunctiva of goats contains epithelial "buds. " The limbal conjunctiva contains no Manz glands but in its place a thickened pig- mented epithelium with rete pegs. The caruncles of sheep and goats are histologically similar. The deep nictitans (Harderian) land is absent in both species. The superficial nictitans gland is simple tubuloalveolar mixed in sheep and compound tubuloalveolar mixed in goats. Microscopically the lacrimal glands resemble the nictitans glands. Many plasma cells are found in the nictitans and lacrimal glands of both species. Six or seven excretory lacrimal du_c_t_s are present in sheep and goats and are lined with stratified columnar epithelium having many goblet cells. Connective tissue septa of the lacrimal gland of sheep contains smooth muscle fibers. The lacrimal passage epithelium 113 114 is stratified: squamous at the puncta, cuboidal to columnar in the canaliculi and columnar with a variable number of goblet cells in the lacrimal sac and nasolacrimal duct. At a few areas pseudostratified columnar epithelium is also observed in the lacrimal sac and naso- lacrimal duct. They are surrounded throughout by a rich venous plexus resembling erectile tissue. A few seromucous glands surround the lOWer third of the nasolacrimal duct. 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