134 RUMINATION. 



posterior the rumen. The lower angle is raised above the 

 level of the third stomach, especially during the action of the 

 gullet and stomachs, so that it is only when the pillars of 

 the canal are at rest, and liquids or soft food descend, or 

 when the contents of the first and second stomach strike 

 against the canal, that any drop into the omasum. 



The fourth stomach, abomasum, is the well-known rennet 

 which, secreting an acid solvent juice, performs a function 

 similar to that of the single stomach in other animals. Its 

 mucous membrane is arranged in folds, transverse at the 

 upper end, longitudinal in the middle, and gradually effaced 

 at the intestinal opening (Fig. 70, B), which is provided with 

 a stout ring of muscular tissue, to prevent the passage of 

 food incompletely digested; hence the name pylorus given to 

 this opening. 



The act of rumination calls into play all the organs men- 

 tioned, with the exception of the abomasum or rennet. It 

 is to a very considerable extent under the control of the will, 

 and any one may observe this by approaching an animal 

 chewing its cud. The process is disturbed and voluntarily 

 recommenced. Tear and any slight disorders stop the act, 

 and although the paunch may contain solid food in its lower 

 pouches, unless the amount is sufficient to be moved by the 

 ordinary rolling action of the organ against the cesophagean 

 canal, rumination cannot go on. 



The coarsely ground food which first enters the paunch 

 and reticulum, is subjected there, for a variable time, to the 

 action of heat and of the liquids contained. These liquids 

 are the saliva, mucus, and secretions of any of the organs 

 themselves. In proportion to the tough nature of the vege- 

 table food is its presence in the rumen prolonged. Liquids, 

 such as the milk of young animals, which need no second 

 mastication, pass chiefly into the second and third cavities; 



