STOMACHS OF RUMINANTS. 55 



on both sides with hard conical papillae hooked upward, 

 and especially prominent towards the free margin of the 

 fold in the vicinity of the passage from the demi-canal to 

 the fourth stomach. Similar hooks with a corresponding 

 direction are found in the lower part of the demi-canal, 

 and all concur in drawing the food upward between the 

 folds and retaining it until sufficiently fine to escape. This 

 organ lies beneath the short ribs on the right side. 



"Fourth Stomach. The fourth or true digesting stomach 

 (rennet, abomasum) is pear-shaped, with the thick end 

 forward, and connected with the manifolds. It extends 

 backward in the right flank along the lower border of .the 

 rumen, and terminates by a narrow opening in the small 

 intestine. It is considerably larger than either the second 

 or third stomach, but incomparably smaller than the first. 

 Its outer surface shows a number of spiral markings run- 

 ning around it longitudinally, and corresponding to exten- 

 sive loose folds of mucous membrane, as observed when it 

 is laid open. Its outer surface is redder and more vascular 

 than that of the other stomachs, but its inner lining or 

 mucous membrane is especially soft, spongy and vascular, 

 forming a marked contrast with the pale, opaque, thick and 

 insensible mucous membrane lining the other stomachs. 

 When magnified, this vascular surface presents throughout 

 a close aggregation of small depressions or alveoli leading 

 into the glandular follicles which secrete the gastric juice. 



" Functions. The progress of food through the different 

 stomachs can now be followed. It is a .wide-spread belief 

 that all food taken by the ox passes first into the rumen, 

 from which it is propelled into the reticulum, is then sent 

 back to the mouth for the second mastication, and is finally 

 swallowed a second time, passing in this case into the third 

 and fourth stomachs. No such regular and invariable 

 course is pursued. After the first mastication, in which 



