294: DIGESTION. 



coat, aided by a brisk, powerful, and involuntary contraction 

 of the abdominal muscles and the diaphragm. Though this 

 act is aided by the contractions of the oesophagus itself, it can- 

 not be accomplished without the action of the diaphragm and 

 abdominal muscles. This has been proven by experiments in 

 which these muscles have been paralyzed ; when rumination 

 becomes impossible. The passage of the bolus from the ru- 

 men to the mouth takes place with great rapidity, and has 

 nothing of the gradual character which is noted in the peris- 

 taltic movements of the intestinal canal. In the rumen, con- 

 trary to the opinion which at one time obtained, the food is 

 only macerated in the fluids which have been swallowed, 

 nothing being secreted in its cavity ; but the position of the 

 reticulum is such as to favor the accumulation in its cavity 

 of fluids, consisting of salivary secretion which has been 

 swallowed, and fluids taken as drink. There is no evidence 

 that there is any fluid secreted in the second stomach. 



"When a bolus is thus brought back to the mouth, it un- 

 dergoes the second mastication, which, in the ox, is gener- 

 ally something less than a minute in duration. At this time 

 it is still further moistened by an abundant flow of saliva, 

 taking place almost entirely from the parotids. 



After the second mastication has been accomplished, the 

 mass is swallowed with great rapidity ; and as it is now 

 soft, and inconsiderable in size, it does not distend the canal 

 which passes from the oesophagus to the third stomach so as 

 to separate the lips and escape into the rumen, but passes di- 

 rectly into the third stomach, or omasum. In the omasum, 

 the food is pressed rather forcibly between the leaf-like folds 

 of the mucous membrane, and gradually passes from this to 

 the fourth stomach, or abomasum, which is the true stomach 

 of these animals, and the only one which secretes the gastric 

 juice. There is no reason to believe that any fluid is se- 

 creted in the third stomach, the contents of which are always 

 remarkably dry. 



The second deglutition is followed very soon by the pas- 



