DIGESTIVE SYSTEM. 193 



inner ones being very scaly and presenting a fibrous- 

 like structure. The submucosa is vascular, with a 

 scattering of small mucous glands, but these form 

 no digestive secretion. Strands of smooth muscle 

 fibers extend into the core of each papilla of the 

 mucosa, also a net- work of blood and lymph vessels. 

 There are two smooth muscle layers, an inner cir- 

 cular and an outer longitudinal, the inner layer 

 being much the heavier. Like the esophagus, 

 these layers show a fine cross-striation, and there is 

 no doubt but that these layers assist in the mechan- 

 ical process of returning the food to the mouth for 

 a more thorough mastication. The serosa is unusually 

 heavy and easily detected in microscopic sections. 



The Reticulum is the second gastric reservoir and 

 is the smallest compartment. Its mucous surface 

 presents a honeycomb appearance when seen from 

 the inside, hence its name. The muscular tunic is 

 thin, otherwise the other layers are analogous to 

 those found in the rumen. 



The Omasum, or third compartment, is only a 

 little larger than the reticulum. The mucous mem- 

 brane is extensively folded to form large leaves ex- 

 tending the length of the organ. Between the 

 large leaves are smaller leaves, and again a third 

 and a fourth series, making altogether about 400 

 laminae of variable sizes. These leaves bear horny 

 papillae, being large and pointed toward the reticu- 

 lum end and small and warty toward the omasum 

 end. These leaves are lined with eight to twelve 

 layers of scaly, tesselated epithelial cells, forming a 

 rough gritty surface. A liberal supply of smooth 

 muscle is present in the center of each leaf, also a 



