396 



DIGESTIVE SYSTEM OF THE OX 



connects the reticulo-omasal opening with the omaso-abomasal opening; it is 

 about three or four inches (ca. 8 to 10 cm.) long, and is directed liackward and a 

 little downward anil to the right. It is free from leaves, but marked usually by 

 slight folds and small ])apilla); it forms a direct path from the reticulum to the 

 abomasum for fluid and finely divided food. In the neck of the omasum there are 

 thick folds, and a number of the peculiar papillae already mentioned as occurring 

 in the lower ])art of the oesophageal groove. The omaso-abomasal orifice (Ostium 

 omaso-abomasicum) is oval, and is about four inches (ca. 10 cm.) long. It is 

 bounded in front by a thick muscular pillar which fades out 

 above on the lateral walls of the omasum. Laterally there 

 are two folds (ValvuliB terminales), which probably prevent 

 regurgitation of the contents of the abomasum. 



The cavity of the abomasum is divided by a constric- 

 tion into two areas. The first of these (fundus gland region) 

 is lined with a soft glandular mucous membrane, which forms 

 about a dozen large, slightly spiral folds (Plicae spirales). 

 The second part (pyloric region) is much narrower and re- 

 sembles in appearance the corresponding region of the horse's 

 stomach. A small cardiac gland zone surrounds the omaso- 

 abomasal orifice. The pyloric orifice is small and round. 



Structure. — The serous coat invests all of the free sur- 

 face of the stomach. The surface of the rumen which is 

 attached to the dorsal abdominal wall is of course uncovered, 

 as well as the adjacent area to which the spleen is attached. 

 The furrows are bridged over by the peritoneum and super- 

 ficial muscle-fibers, and contain fat and (in most cases) 

 branches of the gastric arteries. The lesser omentum passes 

 from the visceral surface of the liver to the right (parietal) 

 face of the omasum and the pyloric portion of the abomasum. 

 There is a fold between the ventral curvature of the omasum 

 and the dorsal curvature of the aliomasum. The great omen- 

 tum is formed by the peritoneum leaving the stomach along 

 the left longitudinal and posterior transverse furrows and the 

 right surface of the rumen below the longitudinal furrow, also 

 the ventral curvature of the abomasum. Its superficial (ven- 

 tral) part is attached on the right to the duodenum, while the 

 deep (dorsal) part blends with the mesentery. It conceals 

 the greater part of the intestine on the right side, with the 

 exception of the duodenum, and covers the ventral sac of the 

 rumen almost entirely. It is not lace-like, as in the horse, 

 and contains a large amount of fat in animals in good condi- 

 tion. The epiploic foramen (of Winslow) is almost sagittal 

 in direction. 



The muscular coat of the rumen consists of an external 



longitudinal, and a thicker internal circular layer. The 



latter forms the bulk of the chief pillars, where it is about one-half to one inch 



(ca. 1 to 2 cm.) tiiick. Scattered bundles of striped muscle-fibers radiate from 



the cardia m the wall of the atrium. 



The muscular coat of the reticulum consists of two chief layers which begin 

 and end at the cesophageal groove; they pass in a circular or oblique fashion 

 around the sac, the fibers of the two layers crossing each other at an acute angle. 

 The walls of the cells contain a central muscular layer. The lips of the oesophageal 

 groove contain a thick layer of longitudinal fibers, which are largely continuous at 

 or cross each other below the reticulo-omasal orifice. The bottom of the groove 



Fig. 291. — MuscuLATunE 



OF GisOPHAGEAL 



Groove and Ad- 

 jacent Part op 

 Stomach of Ox, 



SEEN from with- 

 in after Removal 

 OP Mucous Mem- 

 brane. 



a, CEsophagus; t, in- 

 ner muscular layer of atri- 

 um; d, reticulo-omasal ori- 

 fice; e, e', muscle of lips of 

 groove; g, lower eml of 

 muscle of larger liji, which 

 curves around the reticulo- 

 omasal orifice in part and 

 spreads out in the inner 

 muscular layer of the reti- 

 culum in part; h, lower end 

 of inuscle of smaller lip 

 which in part curves 

 around the reticulo-omasal 

 orifice and is in part con- 

 tinuous with the inner mus- 

 cular layer of the omasal 

 groove and the omasum; 

 t, inner muscular layer of 

 reticulum. (Ellenberger- 

 Baum, .\nat. d. llaustiere.) 



