INTERIOR 459 



ventrally on the right wall of the atrium and reticulum to end at the reticulo- 

 omasal orifice.i It is about seven or eight inches (ca. 18-20 cm.) in length Its 

 axial direction is chiefly dorso-ventral, but it inclines forward to a variable extent 

 and somewhat medially in its ventral part; the ventral end, which is at the reticulo- 

 omasal orifice, is about an inch (ca. 2.5 cm.) in front of the plane of the cardia and 

 to the right of the median plane. The groove is twisted in a spiral fashion, so that 

 Its thickened edges or lips project first backAvard, then to the left, and finally for- 

 ward. The twist involves chiefly the left lip, and the relative position of the lips 

 IS reversed at the ventral end. The mucous membrane on the lips of the oesoph- 

 ageal groove is brown and wrinkled, like that of the atrium; in the bottom of the 



- - interior 



\ 



I 

 \ 



\ 



Fig. 391. — Omasum of Ox, Sagittal Section; Right View. 

 1, 2, 3, 4, Laminae of various orders; 5, muscular pillar; 6, neck coanecting with reticulum; 7, connection with 



abomasum. 



groove it is pale, like that of the cesophagus, marked by longitudinal folds, and pre- 

 sents pointed, horny papilla on its ventral part. 



In the reticulum the mucous membrane is raised into folds about half an inch 

 high, which enclose four-, five-, or six-sided spaces or cells (Cellulse reticuli); this 

 peculiar arrangement suggested the scientific name and also the popular term 

 "honey-comb." These cells are subdivided by smaller folds, and the bottoms are 

 studded with pointed, horny papillae. The cells grow smaller and gradually dis- 

 appear near the oesophageal groove and the edge of the rumino-reticular fold; an 

 inch or two from the latter the mucous membrane has the papillary arrangement 

 of the rumen. At the reticulo-omasal orifice there are peculiar horny papillae, 

 which are curved and resemble the claws of a small bird; hence they are termed 

 ungulif orm (Papillae ungulif ormes) . The reticulo-omasal orifice (Ostium reticulo- 

 1 It might better be termed the sulcus reticuli. 



