DIGESTIVE SYSTEM OF THE SHEEP 405 



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 hes under the upper ends of the last two ribs; the ventral 

 extremity is usually opposite the seventh or eighth rib, al)out 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, l)ut 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 l)are. 



The anterior part of the hard palate is prominent and smooth; on the pos- 

 terior part of this area there arc 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 papillae, many of 

 which are long and sharp-pointed, while others are short and blunt. There is also a 

 series of conical papillae 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 papillse 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 ])ronounced 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 



Ii At birth or first week 1 to 1 3^ years 



Ij First or second week 1 3^ to 2 years 



I3 Second or third week 2J^ to 3 years 



I4 Third or fourth week 33^ to 4 years 



P2 ^ 2 to 6 weeks 13^ to 2 years 



Ml 3 months (lower), 5 months (upper) 



M2 9 to 12 months 



M3 13/^ to 2 years 



