456 DIGESTIVE SYSTEM OF THE OX 



omasum. The greater curvatxxre 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 (Fades 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 

 (Fades 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 (CoUinn omasi) which is the con- 

 nection with the reticulum. 1 



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 cm.) from the 

 anterior extremity of the abomasum. The greater cixrvature 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." The fimdus or anterior extremity forms a rounded blind sac which Hes 

 against the reticulum. The pyloric or posterior extretnity is much smaller and bends 

 upward and forward to join the duodenum. The intermediate part is sometimes 

 termed the body. About six to eight inches (ca. 15 to 20 cm.) 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 oesophagus 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 (Pilae ruminis) ; these are folds of the wall, strengthened by additional 

 muscular fibers, and correspond with the grooves on the outside. The two ex- 



^ 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. 



' Adhesion of the reticulum to the diaphragm is frequently present, but is pathological; the 

 same is true in regard to adhesion to the liver. 



