316 POULTRY PRODUCTION 



of ruminants. It is into this pouch that the feed finds its 

 way. Here it becomes softened and takes on an acid re- 

 action. Although a comparatively profuse secretion is 

 poured into the pouch, it contains no ferments. Its function, 

 if other than storing and softening, is not yet understood. 

 Hard material, like grain, remains in the crop about twelve 

 hours. 



Glandular Stomach. — Beyond the crop the gullet contracts 

 until well within the body cavity, when it expands somewhat 

 to form the glandular stomach (proventriculus), from which 

 it passes immediately into the gizzard (ventriculus bulbosus), 

 an involuntary sphincter muscle separating them. 



The glandular stomach, which is little more than a thick- 

 ening of the gullet wall, does not appreciably detain the feed, 

 but surrounds it with an acid gastric juice which passes with 

 it into the gizzard. It is supplied with but one type of com- 

 plex cells, which secrete pepsin, acid, and a starch-digesting 

 enzyme. The pepsin reduces the proteid to peptones, which 

 are further reduced by the pancreatic juice. Besides fur- 

 nishing the proper medium for the action of the gastric 

 juice, the acid acts as a solvent for such mineral matter as 

 is not in assimilable form, thereby making its absorption 

 possible. 



The Gizzard. — ^The gizzard is oval in form, having two 

 openings on its upper side, one communicating with the 

 proventriculus and the other with the small intestine. It is 

 depressed on each side, being situated behind the liver 

 and partly covered by the lateral lobes of that gland. It 

 is composed of two thick, red, powerful muscles covered 

 internally with a thick, horny epithelium. 



The gizzard is a very efficient crusher. It has been stated 

 that iron tubes capable of supporting a weight of 535 pounds 

 have been completely flattened out by passing through the 

 gizzard of a turkey. This crushing process is absolutely 

 necessary for the digestion of grains, and is most efficient 

 only when aided by the presence of grit and gravel taken in 

 through the mouth and always present in a normal bird. 

 Gastric juice is incapable of digesting the cellulose walls of the 

 grains and does not act until, the grains are reduced by the 



