RUMINATION. 



317 



ruminant animals consists of the following parts: the oesophagus opens 

 into the rumen, or paunch, which communicates by an opening with the 

 reticulum, or water bag, this again with the third stomach, or psalter, 

 omasum, or manyplies, which finally, by a small opening, communicates 

 with the fourth, or true stomach, or abomasum. 



The histological structure of these compartments varies consider- 

 ably. Only the fourth stomach can be compared with that of animals 

 which possess but a simple, single stomach. The rumen is coated with 

 horny epithelial cells, arranged in rows in a manner somewhat similar to 

 the epidermal cells of the skin (Fig. 133). The similarity is further 



Fig. 133.— Section op Wall of the Rumen. (Mlenberger.) 



A, horny layer; B, lower epithelial layer ; C, papilla? ; D. submucous muscular layer ; E, inner muscular 

 coat; F, ganglia; G, external muscular coat ; H, serous coat. 



completed in that the submucous connective tissue in the rumen is also 

 elevated into papillae, similar to those found in the thickness of the skin. 

 It is well supplied with muscles, and the muscular fibres in the sub- 

 mucous layer are tolerably well developed. But few glands are to be 

 found in the rumen, and these are simply of a mucous type, while acinous 

 glands pass through the submucous connective tissue down to the 

 muscular fibres below. The cavity of the paunch or rumen is by far the 

 largest of the four stomachs, and constitutes about nine-tenths of the 

 space represented by the ruminant stomach. 



