STOMACHS OF RUMINANTS. 53 



"(Esophagean Demi-canal Connecting these organs with 

 the gullet on the one hand and the third stomach on the 

 other, is the demi-canal, one of the most interesting struc- 

 tures in the whole economy. It may be conceived of as 

 the lower portion of the gullet, extending from right to 

 left across the superior surface of the anterior left sac of 

 the paunch and the reticulum as far as the entrance of the 

 third stomach. But in place of its forming a perfect tube, 

 as elsewhere, the lower half of its walls is removed so as to 

 leave a large opening of about six inches in length, com- 

 municating with the rumen and reticulum. The margins 

 of this opening are formed of thick pillars, made up largely 

 of muscular tissue, in part forming loops around the ends 

 of the canal, and in part diverging on the walls of the first 

 two stomachs. This muscle encircles the entire ovoid 

 opening, and, when contracted, brings its lips in close 

 opposition, shutting off all communication between the 

 gullet and first two stomachs, and securing a continuous, 

 unbroken passage from the mouth to the third stomach. 

 When, on the other hand, the muscular pillars of the 

 demi-canal are relaxed, the canal remains open, and there 

 is no barrier to communication between the gullet and first 

 two stomachs, or between these stomachs and the third. 



" Third Stomach. The third stomach (manifolds, oma- 

 sum), a little larger than the reticulum in the ox, lies over 

 that organ to its right, and above the right anterior sac of 

 the rumen. Its main characteristic is the leaf -like arrange- 

 ment of its interior. From its walls on the convex aspect 

 twelve or fourteen folds extend quite to the opposite side 

 of the viscus. In the intervals between these are an equal 

 number of folds of about half the length. On each side of 

 these are others still shorter, and so on until the smallest, 

 which appear as simple ridges on the mucous membrane. In 

 this way the flat surfaces of the folds are brought into close 

 relation at all points in place of leaving large intervals at 



