Part 133

In the new-born calf the liver is relatively much larger than in the adult. The visceral surface presents, below the portal fissure, a large rounded eminence, which is caused by the presence in the underlying gland substance of a large venous sinus into which the umbilical and portal veins empty. A large vessel, the =ductus venosus=, leads from this sinus directly to the posterior vena cava. Just external to this elevation is a small but distinct lobe about two inches long (Processus papillaris?). The umbilical fissure is deep and partially divides the gland into two chief lobes.

THE PANCREAS

The pancreas of the ox is irregularly quadrilateral in form, and lies almost entirely to the right of the median plane. Its weight is about the same as that of the horse. Its dorsal surface is related to the crura of the diaphragm, the cœliac and anterior mesenteric arteries, and the liver. It is attached to the liver at and external to the portal fissure, and to the crura of the diaphragm. Between these adhesions it is free and forms the ventral wall of the epiploic foramen (of Winslow). On the right side it extends backward beyond the caudate lobe of the liver between the layers of the mesoduodenum; here it is in contact with the upper part of the flank at the lumbo-costal angle, and is related above to the right kidney and by its ventro-lateral border to the ventral part of the duodenum. The gastro-intestinal or ventral surface is in contact with the dorsal curvature of the rumen and the intestine. The portal vein passes through the gland. The left extremity is small; the right or posterior is wide and thin and is often divided into two branches. The duct leaves the posterior part of the ventro-lateral (or right) border and enters the duodenum about twelve inches (ca. 30 cm.) further back than the bile-duct.

FIG. 300.—SPLEEN OF OX; VISCERAL SURFACE. ]

THE SPLEEN

The spleen has an elongated, elliptical outline, both extremities being thin, rounded, and similar in size.

Its average weight is about 30 ounces (ca. 800 to 900 gm.), or about ⅙ per cent. of the body-weight. Its length is about 16 to 20 inches (ca. 40 to 50 cm.), its width about 5 to 6 inches (ca. 12 to 15 cm.), and in the middle its thickness is about an inch (ca. 2 to 3 cm.).

The =dorsal extremity= lies under the upper ends of the last two ribs; the =ventral extremity= is usually opposite the seventh or eighth rib, about a handbreadth above its junction with the cartilage. The =parietal surface= is convex, and is related to the diaphragm. The =visceral surface= is concave, and is related chiefly to the left face of the rumen, but also usually to a narrow adjacent area of the reticulum. The dorsal part is attached to the left crus of the diaphragm and the left surface of the rumen by peritoneum and connective tissue; the ventral part is free. The hilus is situated on the dorsal third of the visceral surface, near the anterior border.

About one-half of the visceral surface of the spleen is attached directly to the rumen and is not covered by peritoneum; the line of reflection of the latter crosses the surface obliquely, from the upper part of the posterior border to the anterior border a little below the middle. Similarly there is a narrow uncovered area on the upper part of the parietal surface along the anterior border. The hilus is not a groove, but a simple depression. When hardened in situ, the organ is seen to be somewhat twisted, so that the upper part of the parietal surface faces upward and forward, while below it is directed outward.

DIGESTIVE SYSTEM OF THE SHEEP

The =lips= are thin and mobile; the upper one is marked by a very distinct philtrum, and otherwise is not bare.

The anterior part of the =hard palate= is prominent and smooth; on the posterior part of this area there are two narrow depressions in the form of a =V=, at the deep anterior ends of which the naso-palatine ducts open. The ridges of the palate are irregular and their edges are smooth. The posterior third or rather more of the palate is not ridged and presents numerous orifices of ducts of the palatine glands. The mucous membrane is often more or less pigmented.

The mucous membrane of the =cheeks= is covered with large papillæ, many of which are long and sharp-pointed, while others are short and blunt. There is also a series of conical papillæ on the floor of the mouth under the lateral part of the tongue.

The =tongue= resembles that of the ox in form, but the tip is comparatively smooth; the papillæ here are very numerous, but short and blunt. This difference is in conformity with the dissimilarity in the mode of prehension. The prominence of the dorsum is commonly not so pronounced nor so sharply marked off in front as in the ox. The root is smooth. The mucous membrane of the dorsum is often pigmented in spots.

The dental formula is the same as that of the ox. The =incisor teeth= form a narrow and strongly curved arch. The crowns are long and narrow; their labial surfaces are strongly convex and end at a sharp edge which is used in cropping the grass. The roots are more firmly embedded than in the ox.

The =cheek teeth= resemble those of the ox. There is a thinner layer of cement, which is usually black.

The average periods of eruption of the teeth are indicated in the subjoined table.

TEETH TEMPORARY PERMANENT I{1}. At birth or first 1 to 1½ years week I{2} First or second week 1½ to 2 years I{3} Second or third week 2½ to 3 years I{4} Third or fourth week 3½ to 4 years ────────────────────────────────────────────────────────────── P{1} 2 to 6 weeks. 1½ to 2 years P{2} „ „ P{3} „ „ ────────────────────────────────────────────────────────────── M{1} 3 months (lower), 5 months (upper) M{2} 9 to 12 months M{3} 1½ to 2 years

FIG. 301.—STOMACH OF SHEEP, LEFT VIEW.

From photograph of specimen hardened in situ. The reticulum is somewhat contracted. Arrow points to posterior furrow between blind sacs. ]

FIG. 302.—STOMACH OF SHEEP, RIGHT VIEW.

From photograph of specimen hardened in situ. Dotted line indicates position of spleen. ]

The =salivary glands= resemble those of the ox in general, but the parotid duct crosses the surface of the masseter muscle, and opens opposite the third or fourth cheek tooth.

The =tonsil= is bean-shaped and about half an inch (ca. 12 mm.) in length. It does not project into the fauces. The mucous membrane of the latter presents two deep and very narrow tonsillar sinuses on either side.

FIG. 303.—CROSS-SECTION OF SHEEP, THROUGH NINTH THORACIC VERTEBRA, ANTERIOR VIEW.

1, Cardiac orifice; 2, œsophageal groove; 3, rumino-reticular orifice; 4, rumino-reticular fold; 5, dorsal sac of rumen; 6, body of ninth thoracic vertebra; 7, vena hemiazygos; 8, aorta; 9, posterior mediastinal lymph gland; 10, 10, crura of diaphragm; 11, posterior vena cava; 12, portal vein; R.l., right lung; L.l., left lung; S, spleen (cut very obliquely); L, liver; R, reticulum (posterior wall). Arrow points to reticulo-omasal orifice. ]

The fornix of the =pharynx= presents a median plicated fold which is a continuation of the septum nasi. The pharyngeal orifice of the Eustachian tube has the form of a crescentic slit, placed about on a level with the inferior nasal meatus. There are two large lymph glands and a number of hæmolymph glands above the pharynx.

The =œsophagus= has a lumen of about an inch when moderately distended; otherwise it resembles that of the ox.