CHAP. XIII.] THE PROCESS OF RUMINATION. 479 



membrane of this cavity is thrown into the form of a number of leaves, 

 projecting far into the lumen of the sac, and these are covered with small 

 button-shaped" papillae, and by a layer of stratified pavement epithelium. 

 This sac has in its walls involuntary muscular fibres forming strong longi- 

 tudinal and circular layers. A layer of fibres also exists in the centre of 

 each leaf or fold, in addition to a t. muscularis mucosce. The structure of 

 the abomasum or true stomach is like that described as characterising the 

 stomach of man or the dog ; it contains glands of the fundus and glands of 

 the pylorus, and the mucous membrane is covered by cylindrical epithelium. 

 'The lower end of the oesophagus opens into the paunch, but at the 

 left side a deep groove runs along the inner wall of the reticulum, from 

 the entrance of the oesophagus into the paunch to the entrance of the 

 reticulum into the psalterium. This may be called an cesophageal canal 

 or groove. To understand its true relations we may regard the paunch 

 and the reticulum as diverticula, or sacs developed from the lower wall of 

 the oesophagus, and the psalterium as a diverticulum from the upper wall, 

 supposing the animal to be on all fours in its normal position. We are 

 now in a position to understand rumination V 



The process The solid matters of the food, which have been 

 tion'' r mina " subjected to the first or preliminary mastication, toge- 

 ther with nearly the whole of the liquids (saliva and 

 water), pass, after deglutition, into the reticulum, which is the real 

 centre of the group of cavities which constitute the gastric apparatus 

 of the ruminant. In virtue of its central position and of its power- 

 fully muscular walls, the reticulum can divert the matter which flows 

 into it either towards the right, into the rumen, of which it forms a 

 preliminary chamber, or towards the left, into the psalterium and true 

 stomach. The reticulum, in fact, in so far as the products of the first 

 mastication are concerned, serves as a distributor of its products ; in 

 its cavity it stores only a certain part of the fluid which has reached it. 

 During rumination, the solid matters which have been stored in 

 the rumen are, by the contractions of the rumen and through the 

 instrumentality of the reticulum, regurgitated along the oesophagus 

 into the mouth, in order to be subjected to a second and more perfect 

 process of mastication (' chewing the cud '). When again swallowed, 

 the finely comminuted alimentary particles, mixed with the saliva, pass 

 along the cesophageal gutter directly into the psalterium. In this 

 division of the stomach the comminution of the digested food is com- 

 pleted and it acts as a feeder and a regulator of the supply of matters 

 in respect to the fourth or true stomach in which the real process of 

 peptic digestion has its seat. 



The chemical mucous membrane of the rumen, as could be 



processes deduced from its structure (for it possesses no glands 



which have and is lined by stratified squamous epithelium), forms 

 their seat in no secretion. In the rumen, the partially masticated 

 ve o eta bl e matter is subjected, under the most favour- 

 able conditions of temperature, to the prolonged action 



1 J. G. McKendrick, A Text-book of Physiology, Vol. n. pp. 100, 101. 



