KTJMINATION. 327 



lubricating function lias been served, is again swallowed. This fluid 

 consists partially of saliva and water, or, in other words, the contents of 

 the rumen and reticulum, and as the bolus of food enters the oesophagus 

 this fluid is mechanically driven in with it. Its presence is absolutely 

 essential to the act of rumination, for rumination is impossible in animals 

 when deprived of water, or in whom the secretion of saliva has been 

 interfered with. 



As soon as the cud reaches the pharynx the soft palate suddenly 

 rises and the food is carried by the tongue between the molar teeth and 

 cheeks, the mechanism by which the food is prevented from entering the 

 nasal chambers and larynx being precisely the same as has already been 

 described as taking place during deglutition. The amount of food 

 raised in each bolus varies from one hundred to one hundred and twenty 

 grammes. It is at first only coarsely ground, and not very soft or fluid, 

 but it soon becomes fine and comminuted and thoroughly macerated in 

 the second mastication, and is collected in a little cake on the back of 

 the tongue preparatory to swallowing a second time. Since the quantity 

 composing each bolus may be readily determined by withdrawing the 

 cud from the mouth as soon as it is rejected from the stomach, it is 

 possible to calculate how many of these rejections are necessary for the 

 mastication of the twelve to fifteen kilos of ha}' which constitute the 

 ordinary daily ration of an ox. Since it has been shown that dry fodder 

 absorbs in mastication and in the rumen four times its own weight of 

 fluid, twelve thousand five hundred grammes of hay will acquire a 

 weight of sixty-two thousand five hundred grammes. It is, therefore, 

 necessary that five hundred and twenty rejections, each of one hundred 

 and twenty grammes, take place. In order to permit all of this food to 

 undergo a second mastication, and as each bolus requires about fifty 

 seconds for its second mastication, at least seven hours would be 

 required for the process of rumination ; even if we admit that one- 

 seventh of the food is not masticated a second time, one-fourth the day 

 is required for rumination. The ox, therefore, cannot, like the horse, 

 be used for constant effort, as he requires time for rumination, and, as 

 will be shown directly, rumination is very readily interfered* with by 

 any active exertion. 



As soon as the bolus enters the mouth it is subjected to a second 

 mastication, which differs from the first only in being more regular and 

 more complete. The number, rapidity, and regularity of the movements 

 of the jaw in this second mastication appear, however, to be subject to 

 numerous variations. As already stated, the movements of the jaws are 

 unilateral; this also applies to the second mastication, although perhaps 

 less regularly. Unilateral rumination is seen in the ox, sheep, giraffe, 

 antelope, and other animals, and is most usual. Its duration may be as 



