THE ANATOMY OF THE OX. 66 



from which it is separated by a slight constriction. The cavity 

 of the omasum opens on the one side into the second, and on 

 the other side into the fourth, compartment. In the interior are 

 numerous leaves or folds of the mucous membrane. They are 

 really lengthened elevations of the mucous membrane, each 

 being formed of two layers of membrane lying against and rather 

 close to each other. They are arranged transversely, and 

 follow the long axis of the organ. They vary from 100 to 

 130 in number. They are not equal in size. By one border 

 they are attached to the great curvature of the cavity. The 

 other border is concave and free, and it is turned towards the 

 lesser curvature. These folds resemble the leaves of a book, 

 and they are provided with small hooks for catching the 

 food which has escaped mastication. As we have said above, 

 the cavity is ovoid in shape, and hence the central leaves are the 

 longest and largest. Between each pair of large leaves inter- 

 mediate and small leaves are placed, but these extend only a 

 little distance. The leaves are formed of an inner framework of 

 muscular fibres. This is covered on both sides with mucous 

 membrane which is elevated to form papillse. Some of these 

 papillae are large and bent, and retain portions of food which 

 need to be more strongly triturated, while other papillae are 

 small. The fluid and finer particles of food pass on into the 

 abomasum. At the entrance of the cesophageal canal the papillae 

 are large and hooked. The use of these papillae may be to 

 retain the alimentary material in the cavity, and for this purpose 

 also the omasum has a small valve at the oritice which leads to 

 the abomasum, or fourth stomach, which we now proceed to 

 describe briefly. 



The abomasum or rennet or reed is the true digestive stomach. 

 In regard to capacity, the abomasum comes next in size after 

 the rumen. It is situated behind and on the right side of the 

 manyfold, and is especially large in the young animal. When 

 removed and dried, the stomach in the calf is termed the rennet. 

 It is used to coagulate milk in making cheese, for it contains 

 the gastric glands, i.e. the glands which secrete the gastric juice, 

 and this fluid acts on the caseine of milk and coagulates it. 

 The mucous membrane lining this stomach is villous, velvety, 

 soft, vascular, and of a reddish hue. The velvety or villous 

 nature of the lining is caused by numerous tiny irregular pro- 



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