lO 



about 8 cm. dorsal to the costo-chondral junction, the diaphragm and omen- 

 tum are the only structures that intervene between the omasum and the 

 abdominal wall. The visceral or left surface of the omasiun is related to 

 the rtimen, reticulum and abomasum, Pis. IV and VIII. Dorsally the 

 omasum is related principally to the liver, pancreas, small and large in- 

 testines. The ventral surface of the omasum is in contact with the abo- 

 masum and abdominal floor, PI. VIII. The cavity of the omasum is oc- 

 cupied largely by a series of longitudinal folds or laminae which depend 

 from the dorsal and lateral walls of the compartment. One hundred and 

 sixty of these folds or laminae were counted. They vary in width from 

 a few millimeters to 20 or 25 cm. Of these one hundred sixty laminae, 

 sixty-four were from 2 to 4 mm. up to i cm. or 1.5 cm. in width; fifty-six 

 were from 1.5 cm. to about 3.5 cm. in width; twenty-eight were from 

 about 3.5 cm. to 14 cm. in width ; and twelve were from 14 cm. to 22 cm. 

 in width. 



The abomasum or fourth compartment of the stomach is an elongated, 

 piriform structure sharply flexed toward its smaller or pyloric extremity. 

 It lies on the floor of the abdomen to the right of and somewhat ventral to 

 the rumen. Its cephalic end is opposite the costo-chondral junction of the 

 seventh rib. From here it extends in a direction more or less obliquely to 

 the right, some distance along the floor of the abdomen, and then makes a 

 sharp flexure of about 180 degrees and extends cephalo-dorsad to opposite 

 the ventral part of the tenth (or ninth) intercostal space on the right side, 

 Pis. II, III, IV, also PI. VIII. The most caudal point of the greater cur- 

 vature reaches a transverse vertical plane through the umbilicus. The 

 larger portion of the abomasum is situated to the right of the median plane, 

 but a portion of it lies to the left of this plane. In the specimen from 

 which Pis. I to VII were made the abomasum was visible on the left side 

 nearly as far back as the umbilicus, Pis. V to VII. In other specimens the 

 abomasum was visible upon removal of the left wall of the abdomen, but not 

 to so great an extent as shown in plates V to VII. The parietal (ventro- 

 dextral) surface of the abomasum for the most part lies upon the floor of 

 the abdomen, a small part only being in contact with the right abdominal 

 wall. The visceral (dorso-sinistral) surface is in contact with the ventral 

 sac of the rumen, the omasum and the small intestine. The cephalic end 

 is closely attached to the reticulum. The abomasum has two curvatures 

 — • greater and lesser. The greater curvature is ventro-caudal and to it 

 are attached the greater omentum and the cephalic end of the ventral sac 

 of the rumen. The greater part of the lesser or dorso-cephalic curvature 

 of the abomasum is attached by connective tissue and peritoneum to the 



