338 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



gradual passage into the small intestine, with the consideration of the 

 influence of the nervous system. These steps in the process of diges- 

 tion often become characteristic of gastric digestion in the different 

 domestic animals. 



If abstinence has continued for some time, the stomach will have 

 emptied itself .of its contents more or less completely, and contracted so 

 as to obliterate its cavity in different degrees according to the different 

 species of the animals. In the dog and other carnivora, after abstinence 

 has continued for twenty-four or forty-eight hours, the stomach will be 

 found to be contracted to a small volume, and will be irregular and ovoid 

 in shape. Its mucous membrane will be thrown up into folds and its 

 cavity almost obliterated, while the reaction of its mucous secretion will 

 be neutral, or even alkaline. In omnivorous animals, such as the pig, 

 the stomach does not contract so completely, nor does it ever become 

 entirely emptied, but will, even after prolonged abstinence, be found to 

 contain a bilious liquid and fetid gases. In the horse, after prolonged 

 fasting, the distinction between the right and left half of the stomach 

 becomes more marked. The right half of the stomach behaves in these 

 respects almost like the stomach of the carnivora and becomes highly 

 contracted, with its cavity almost obliterated. The left portion of the 

 stomach, on the other hand, remains dilated and will nearly always be 

 found to contain saliva which is swallowed during abstinence. When 

 food enters the stomach after prolonged abstinence, it dilates insensibly 

 and changes its positions and relations. In the fasting condition the 

 pylorus sinks, and the stomach tends to assume, in this state of func- 

 tional inactivity, a position in the direction of the long axis of the body, 

 corresponding more or less with what is its normal state in lower groups 

 of animals, in whom the stomach is of minor importance. When food 

 accumulates t in the stomach the pylorus rises, and the organ now occu- 

 pies a position at right angles to the axis of the body, while it rotates on 

 its own axis so as to cause the greater curvature of the stomach, which 

 in the position of rest is directed downward and to the left, in the state 

 of repletion of the organ to become transverse and directed anteriorly 

 (or downward in quadrupeds). 



The mode of accumulation of food in the stomach varies according 

 to the character of the material swallowed. Soft and diffluent foods and 

 liquids will mix at once, and if the food is swallowed in voluminous 

 masses, as in the carnivora, or dry or in more or less firm boluses, as 

 in the herbivora feeding on dry fodder, and in the non-ruminants, the 

 first portions which enter the empty stomach are deposited in the cardia. 

 Those which go afterward push these toward the greater curvature and 

 toward the pylorus, while liquids and softer food fill up the interstices 

 between them. 



