DOMESTfC ANIMALS 



27 



feed may remain for a long time in the 

 paunch and is then more easily regur- 

 gitated. In forming a cud from the 

 coarse material in the paunch and ele- 

 vating it to the mouth the first two 

 stomachs seem to co-operate, but the ab- 

 dominal muscles and diaphragm furnish 

 the necessary force. If the abdominal 

 muscles are paralyzed, rumination is 

 impossible. When the cud reaches the 

 mouth it is prevented by the soft palate 

 from entering the nasal chamber in the 

 roof of the mouth. The mastication of 

 a cud may be prolonged for fifteen min- 

 utes. The cud is then swallowed and an- 

 other ascends to the mouth within 



which the material is not discharged 

 from the mouth. Owls and other car- 

 nivorous birds voluntarily vomit up the 

 bones and hair of their prey after the 

 meat is digested. Various other birds 

 can easily reject the contents of their 

 crop, and in the case of pigeons partly 

 digested material is brought up from the 

 crop to feed the young birds. 



Vomiting as ordinarily understood, 

 however, is an involuntary and patho- 

 logical process. Dogs and cats vomit 

 very readily, pigs with difficulty, and 

 horses very rarely or not at all. In the 

 horse the stomach is small and cannot 

 be easily grasped by the abdominal mus- 



Fig. 18 CHAMPION LEICESTEB AT RECENT INTERNATIONAL FA' 



:K SHOW AT CHICAGO 



about four seconds. The masticated 

 cud after being swallowed ] 

 through the opening between the second 

 and third stomachs and thence into the 

 fourth or true digestive stomach. Ru- 

 mination is impossible if the paunch is 

 not fairly well distended with food. 

 The process appears to be voluntary but 

 is partly a reflex, unconscious action, 

 performed as a rule while lying down. 

 Rumination is interrupted by fright, 

 pain or disease, and this well known fact 

 has given rise to the fallacy that such 

 animals have 'lost their cud." 



Rumination may be regarded as a reg- 

 ulated, voluntary process of vomiting in 



cles so as to force its contents upward. 

 Reproduction _ The physiological 

 processes thus far discussed are con- 

 cerned with the preservation of the in- 

 dividual. "VTe may now refer briefly to 

 the essential features of reproduction 

 or preservation of the race. In all 

 birds and mammals the female repro- 

 ductive elements are eggs produced in 

 ovaries while the male elements are 

 spermatozoa produced in testicles. The 

 egg is fertilized by the union of a sper- 

 matozoon with it and at once begins to 

 develop. In birds the egg is fertilized 

 at or near the ovary after which the 

 white of the egg, shell membrane and 



