THE PELVIC CAVITY—THE STOMACH 453 
ribs, or through the last thoracic vertebra. The chief differential features in the 
arrangement of the peritoneum will be described with the viscera. The sub- 
peritoneal tissue is more abundant than in the horse, and in general contains a 
much larger amount of fat. 
THE PELVIC CAVITY 
The pelvie 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 pubic part of the floor is about horizontal, 
but the ischiatic part slopes dorsally to a marked degree; this part is also deeply 
coneave 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 occunies 
nearly three-fourths of the abdominal cavity. It fills 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, and consists of four divisions, viz., rumen, reticulum, omasum, 
and abomasum.! The division is clearly indicated externally by furrows or con- 
strictions. The first three divisions are often regarded as proventriculi or cso- 
phageal sacculations, the fourth being the stomach proper (in the narrower sense 
of the term). The cesophagus opens into the stomach on a sort of dome, the 
atrium ventriculi, and is continued through the reticulum by the cesophageal 
groove. From the ventral end of the latter a groove traverses the ventral wall of 
the omasum, thus giving a direct path from the reticulum to the abomasum for 
finely divided food or fluid. The abomasum joins the small intestine. 
Capacity.—The capacity of the stomach varies 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 correlation with the nature of the food. In the new-born calf the rumen and 
reticulum together are about half as large as the abomasum; in ten or twelve weeks 
this ratio is reversed. During this period the omasum appears to be contracted 
and functionless. At four months the rumen and reticulum together are about 
four times as large as the omasum and abomasum together. At about one and one- 
half years the omasum equals or approaches closely the abomasum in capacity. 
The four divisions have now reached their definitive relative capacities, the rumen 
constituting about 80 per cent., the reticulum 5 per cent., the omasum 7 or 8 per 
cent., and the abomasum 8 or 7 per cent. of the total amount. 
EXTERIOR AND RELATIONS 
The rumen occupies almost all of the left half of the abdominal cavity, and 
extends considerably over the median plane ventrally and in its middle. It is 
somewhat compressed from side to side and may be described as haying two sur- 
faces, two curvatures or borders, and two extremities. The parietal (or left) 
surface (Facies parietalis ) is convex and is related to the diaphragm, left wall of 
the abdomen, and spleen. It extends from the ventral part of the seventh inter- 
costal space almost to the pelvis. The visceral (or right) surface (Facies visceralis) 
is somewhat irregular, and is related chiefly to the omasum and abomasum, the 
1Jn popular language these are regarded as so many stomachs, and are often designated 
numerically. Other names are in common use, e. g., paunch, honeycomb, manifold or manyplies, 
and rennet or true stomach. 
