390 DIGESTIVE SYSTEM OF THE OX 



for some distance. There are submucous glands in the first part of the tube. There 

 is no terminal dilatation, and no part in the abdominal cavity. 



A very large mediastinal lymph gland lies above the posterior part of the oesophagus and 

 may, if enlarged, obstruct it (Fig. 289). 



THE ABDOMINAL CAVITY 



The abdominal cavity of the ox is very capacious, both absolutely and rela- 

 tively, as compared with that of the horse. This is due to several factors. The 

 lumbar portion of the spine is about one-fourth longer than that of the horse. The 

 transverse diameter between the last ribs is greater. The costal attachment of the 

 diaphragm is almost vertical in direction from the lower part of the ninth rib to 

 the extreme upper part of the thirteenth; in fact, the attachment to the last rib 

 is not constant. Thus the abdomen is increased at the expense of the thorax, and 

 the last three or four ribs enter more largely into the formation of the abdominal 

 wall than in the horse. The flank is also much more extensive. The ilia, on the 

 other hand, do not extend forward beyond a transverse plane through the middle 

 of the last lumbar vertebra. The epigastric and mesogastric regions would be 

 separated by a plane through the lower end of the tenth pair of ribs, or through the 

 last thoracic vertebra. The chief differential features in the arrangement of the 

 peritoneum will be described with the viscera. 



THE PELVIC CAVITY 



The pelvic cavity is relatively long and narrow. The inlet is more oblique 

 than that of the horse; it is elliptical in outline, and the transverse diameter is 

 smaller than that of the horse. The anterior (pubic) part of the floor is about 

 horizontal, but the posterior (ischial) part slopes upward and backward to a marked 

 degree; this part is also* deeply concave transversely. The roof is concave in 

 both directions. The peritoneum extends backward as far as the first coccygeal 

 vertebra, so that the retroperitoneal part of the cavity is short. 



THE STOMACH 



General Arrangement. — The stomach of the ox is very large, and occupies 

 nearly three-fourths of the abdominal cavity. It fills all of the left half of the cavity 

 (with the exception of the small space occupied by the spleen) and extends con- 

 siderably over the median plane into the right half. 



It is compound, being composed of four divisions, viz., rumen, reticulum, 

 omasum, and abomasum/ The division is clearly indicated externally by furrows 

 or constrictions. The first three divisions may be regarded as proventriculi or 

 a?sophageal sacculations, the fourth being the stomach proper (in the narrower 

 sense of the term). The cesoiihagus opens into the stomach on a sort of dome 

 formed by tlie rumen and reticulum, and is continued through the latter by the 

 oesophageal groove. From the ventral end of the latter a groove traverses the 

 ventral wall of the omasum, thus giving a direct path to the abomasum for finely 

 divided or fluid food. The abomasum joins the small intestine. 



Capacity. — The capacity of the stomach ^'aries greatly, depending on the age 

 and size of the animal. In cattle of medium size it holds 30 to 40 gallons, in large 

 animals 40 to 60, in small 25 to 35. The relative sizes of the four parts vary with 

 age. In the new-born calf the rimien and reticulum together are about half as 



' In popular language llu^sc arc conveniently regarded as so many stomachs, and teimcd 

 accordingly "first," "second," etc. Other names are in common use, e. g., paunch, honeycomb, 

 manifold or manj'plies, and rennet or true stomach. 



