THE DIGESTIVE SYSTEM. 251 



pylorus has a well- developed spliincter. There are various 

 theories as to the act of rumination, and the manner in 

 which the different cavities are related to this and other 

 digestive processes. A full account of the various views 

 is given in Colin's ' Physiologie Comparee/ Rumination 

 comprises the production of a pellet of the slightly masti- 

 cated food which for some time has been macerating in 

 the rumen, its regurgitation through the oesophagus and 

 pharynx into the mouth, its mastication, and redeglutition. 

 The matter is complicated by the fact that one portion of 

 food is regurgitated a variable number of times, depending 

 on the amount of preparation it requires. Liquids and 

 pultaceous material pass at once into the omasum as well 

 as into the rumen and reticulum. Coarse food may be 

 remasticated as many as four or five times. Until 

 thoroughly softened it passes from the oesophagus indif- 

 ferently into the rumen or reticulum. When the rumen 

 is occupied by a sufficient amount of food it exerts a 

 churning and to-and-fro movement, whereby the alimen- 

 tary matters undergo a certain amount of division, and are 

 thoroughly intermingled with the large quantity of saliva 

 which is poured down from the mouth; so the contents 

 are softened and undergo those changes which are due to 

 thorough insalivation. There is a considerable depth of 

 rumen cavity below the edge of the septum which separates 

 it from the reticulum ; the most fluid portions of the 

 contents of the rumen most readily pass over this *^ high- 

 water mark," so the contents of the reticulum are very 

 fluid. The muscular bands of the rumen are so arranged 

 that when they contract they concentrate the organ, as 

 it were, towards the terminal extremity of the oesophagus. 

 At the same time contraction of the reticulum also occurs, 

 and thus the alimentary material is pressed into the 

 lower end of oesophagus, and passed upwards in pellets 

 into the mouth. Such is the arrangement of this 

 oesophageal groove that, when its longitudinal bands 

 contract, they tend to place the terminal opening of 

 the oesophagus and the opening into the omasum 

 opposite each other, connected practically by a canal 



