RUMINATION. 



319 



The third stomach, or psalter, omasum, or many plies, is situated on 

 the right side of the rumen and reticulum, descending from before back- 

 ward, and is lined by mucous membrane, disposed in broad folds 

 (Fig. 135). These folds are of varying breadth, from twelve to fifteen 

 in number, and form almost complete partitions ; between them are others 

 gradually diminishing in size. The external surface of the mucous 

 membrane of these folds is coated with an epithelial layer, which, when 

 the rumen is not entirely fresh, is readily stripped off. Below this layer, 



FIG. 135. OMASUM AND ABOMASTJM OF THE Ox, LAID OPEN. 



A, omasum, or manyplies. showing its folds: B, the opening communicating with the reticulum. or honey-comb bag; C, 

 aboiuasuin, the true digestive stomach, opened to show the plicae, D, of its mucous membrane. 



which is called the horny layer, comes the mucous membrane proper. It 

 is also provided with papillae, which are larger and thicker than those 

 found in the reticulum. The mucous membrane consists of connective 

 and elastic tissue-fibres and blood-vessels. In the mucous membrane are 

 also found oblique muscular fibres of the unstriped variety. Glands are 

 entirely absent. The folds of the mucous membrane are papillated on 

 the surface, the eminences being flattened on the side and pointed at the 



