SENSE ORGANS AND INTEGUMENT OF THE PIG 777 



long, slender papilla;; in the body of the horn it becomes thin and the papillae 

 are smaller, but increase in size apically. Rudimentary papillated laminae also 

 occur. 



The skin of the sheep varies in thickness from 0.5 to 3 mm., l)ut differs greatly 

 in fineness and in other respects in various breeds. In Merinos considerable 

 folds occur on the neck. Cutaneous pouches (Sinus cutis) are constantly present 

 in certain situations. The infraorbital or lacrimal pouch (Sinus cutaneus infra- 

 orbitalis) is an invagination about half an inch in depth, which is situated in 

 front of the inner angle of the eye. It bears scattered fine hairs, into the follicles 

 of which large compound sebaceous glands open; coil glands are also present. The 

 secretion of the glands is fatty and forms a yellow sticky covering on the skin when 

 dry. The inguinal (or mammary) pouch (Sinus cutaneus inguinalis) is much more 

 extensive, and is situated in the inguinal region in both sexes. The skin of the 

 pouch bears scattered fine hairs and contains well-developed sebaceous glands and 

 exceedingly large coil glands. The interdigital pouch (Sinus cutaneus interdigi- 

 talis) is a peculiar tubular invagination of the integument which opens at the an- 

 terior part of the interdigital cleft. On sagittal section it appears as a bent tube, 

 an inch or more (ca. 2.5 to 3 cm.) in length, and about a fourth of an inch (ca. G 

 to 7 mm.) in diameter. The pouch extends downward and backward, and then 

 curves sharply upward between the distal ends of the proximal phalanges. Its 

 deep blind end is somewhat ampullate. The subcutis forms a capsule around it. 

 The skin of the pouch is thin and pale; it bears fine colorless hairs, the follicles of 

 which receive the secretion of several sebaceous gands. The coil glands here are 

 compound and very large; they open into the hair-follicles or directly into the pouch. 

 The secretion of the glands is a colorless fatty substance. The skin is covered in 

 great part by wool, which is similar in structure to hair, but is finer, curly, and 

 usually contains no medullary cells. The follicles of the wool are curved, and are 

 arranged more or less distinctly in groups of ten or a dozen, several of which open 

 in common on the surface. A considerable part of the face and the limbs is covered 

 with short, stiff hair, and long hairs occur more or less interspersed among the wool. 

 The claws resemble those of the ox. The horns, when present, are more or less 

 prismatic, distinctly ringed, and vary in length and curvature in different breefls. 

 Their structure is similar to those of the ox. 



The olfactory and gustatory organs resemble in general those of the horse. 



SENSE ORGANS AND INTEGUMENT OF THE PIG 

 THE EYE 



The posterior part of the orbital margin is formed chiefly by the orbital liga- 

 ment, which extends from the extremely short supraorbital process to the small 

 eminence at the junction of the malar and the zygomatic process of the temporal. 



Cilia occur only on the upper eyelid. The inner canthus is prolonged l)y a 

 groove on the infraorbital region. The tarsal glands are very short and curved. 

 The conjunctival epith(4ium is of the transitional type with many goblet cells. 



The deep part of the cartilage of the third eyelid is broad and spoon-like, the 

 superficial part somewhat anchor-shaped. In addition to the gland which sur- 

 rounds the deep part of the cartilage, there is a deeper gland of Harder (Glandula 

 palpebrae tertia? profunda), which is surrovmdcd by a distinct capsule and a blood- 

 sinus. This gland is l)rovvnish or yellowish-gray in color, elliptical in outline, and 

 about an inch (2 to 3 cm.) in length. It is situated deeply below the attachment of 

 the inferior oblique muscle. 



