456 DIGESTIVE SYSTEM OF THE OX 
omasum. The greater curvature faces to the left and ventrally; it lies against the 
diaphragm, opposite the sixth and seventh ribs. The ventral extremity forms a 
rounded cul-de-sac, which is in contact with the sternal part of the diaphragm, the 
liver, omasum, and abomasum; it may be termed the fundus reticuli. 
The omasum is ellipsoidal in form and somewhat compressed laterally. It is 
very clearly marked off from the other divisions. It is situated almost entirely 
to the right of the median plane, opposite the seventh to the eleventh ribs. The 
parietal (right) surface (Facies dexter) lies against the diaphragm, liver, and lateral 
wall of the abdomen. The contact with the latter extends over a small area only 
(ventral part of eighth, ninth, and tenth ribs usually). The visceral (left) surface 
(Facies sinistra) is in contact with the rumen and reticulum. The greater curvature 
is directed dorsally and somewhat backward; it is convex, and is related to the 
diaphragm, liver, and intestine. The ventral (lesser) curvature is concave, and 
faces ventrally and somewhat forward; it is in contact with the abomasum chiefly, 
the junction with the latter appearing as a constriction near the middle of the 
curvature; at its anterior part there is a neck (Collum omasi) which is the con- 
nection with the reticulum.! 
The abomasum is an elongated, piriform sac, which lies for the most part on 
the abdominal floor, to the right of the reticulum and the ventral sac of the 
rumen. Its narrow posterior part is strongly curved, the concavity being dorsal. 
The parietal (right) surface lies against the abdominal wall from a point opposite to 
the seventh or eighth rib as far back as the eleventh or twelfth costal cartilage. The 
visceral (left) surface is related chiefly to the ventral sac of the rumen. The lesser 
curvature is dorsal, and is in contact with the omasum; the junction of the two sacs 
is indicated by a constriction about four or five inches (ca. 10 to 12 em.) from the 
anterior extremity of the abomasum. The greater curvature is ventral, and rests 
on the abdominal wall from the xiphoid cartilage to the ventral part of the last 
(right) intercostal space; its direction is approximately parallel to the right costal 
arch.2. The fundus or anterior extremity forms a rounded blind sae which lies 
against the reticulum. The pyloric or posterior extremity is much smaller and bends 
upward and forward to jom the duodenum. The intermediate part is sometimes 
termed the body. About six to eight inches (ca. 15 to 20 em.) from the pylorus there 
is a constriction which marks off the pyloric part from the body and fundus. 
The rumen is attached by peritoneum and connective tissue to the crura of 
the diaphragm and left psoas muscles, from the hiatus cesophagus backward to 
the fourth or fifth lumbar vertebra. 
A small area of the anterior part of the right face of the rumen is adherent to 
the adjacent surface of the abomasum. The greater part of the ventral curvature 
of the omasum is attached by connective tissue to the dorsal face of the abomasum.® 
The lesser omentum attaches the right face of the omasum and the pyloric 
part of the abomasum to the visceral surface of the liver. 
INTERIOR 
The cavity of the rumen is partially divided into dorsal and ventral sacs by 
the pillars (Pile ruminis); these are folds of the wall, strengthened by additional 
muscular fibers, and correspond with the grooves on the outside. The two ex- 
1 The relative size of the omasum is subject to considerable variation. It may extend back 
to a point opposite the ventral fourth of the twelfth rib. The ventral curvature is usually opposite 
to the ninth, tenth, and eleventh costal cartilages, but in some subjects it faces chiefly forward and 
is opposite to the ventral third of the eighth or ninth rib. 
° The greater curvature may be in contact in part with the costal arch, but is chiefly medial 
and ventral to it. It usually bends dorsally near the last costal cartilage and runs upward and 
forward to the eleventh intercostal space. 
8 Adhesion of the reticulum to the diaphragm is frequently present, but is pathological; the 
same is true in regard to adhesion to the liver. 
