86 PRINCIPLES OF VETERINARY SCIENCE 



ments occur: The soft palate is shortened and is raised so as to 

 close the openings into the nasal cavity. The pharynx is short- 

 ened and its end toward the mouth is dilated. The root of the 

 tongue and the larynx are brought toward each other, so that the 

 epiglottis touches the former. The arytenoid cartilages of the 

 larynx are approximated and the glottis is closed, thus preventing 

 aspiration of food particles. The bolus of food is "shot," so to 

 speak, through the pharynx by an energetic contraction of the 

 muscles which raise the tongue. This is followed by a so-called 

 "clearing up" phase in which remnants that remain are removed 

 from the pharynx by the constrictor muscles of that organ. Fluids 

 are "squirted," through the pharynx. The first stage of deglu- 

 tition is voluntary, but the rest of the act is not under the 

 control of the will. 



The movements of the stomach oi the horse are not so exten- 

 sive or of the "churning" type, as was the opinion before experi- 

 ments by Ellenberger were carried out. He showed that the 

 stomach- of a horse fed in the ordinary manner is never empty 

 and consequently does not have a period of rest as does that of 

 man and the dog. Gastric movements must coincide with gas- 

 tric digestion, which is a continuous process, but probably they 

 are greater after a full meal. In view of the fact that the pylorus 

 is usually open, it seems apparent that ingesta are] continually 

 passing into the intestine. 



The rumen of the compound stomach of cattle contracts two 

 or three times per minute. The contractions are stronger and 

 more frequent during feeding, when the ingesta are moved in all 

 directions thoroughly to mix them, and for a period after feeding, 

 when the process of rumination is taking place. They may be 

 felt by pressing with the palm of the hand gently but firmly in 

 the left flank. 



Rumination consists of the return of portions of ingesta from 

 the rumen and reticulum to the mouth, where it undergoes 

 thorough mastication and insalivation, and is again swallowed. 

 The process is repeated at intervals of six or eight hours and 

 occupies about one-fourth of the animal's time. It is under the 

 control of the will and usually begins about half an hour after 

 feeding. If a cow that is chewing her cud is suddenly disturbed, 

 the process ceases but can be resumed when she recovers her 

 composure. According to Sisson the mechanism of regurgitation 



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