DISEASES OF POULTRY. 



85 



cuius is slight, and with those birds which live upon 

 vegetable substances the food is fed to it gradually 

 and almost constantl}' from the crop. Birds which eat 

 insecls. fruits, or flesh exclusively have either no crop 

 or only a simple dilatation of the oesophagus, as such 



food is easilj' digested. 



Eagle. 



Gannet. 



In the w^alls of the pro- 

 ventriculus are the gas- 

 tric glands which secrete 

 the gastric j nice required 

 for the digestion of the 

 albuminoid constitu- 

 ents of the food. The 

 different forms assumed 

 by the gastric glands 

 in various species of 

 birds are illustrated in 

 Fig. 16. The simplicity 

 or complication of these 

 glands indicates to a 

 certain extent the kind 

 of food which is natu- 

 ral to the species. The 

 gastric juice may digest 

 flesh, fish, and ground 

 feed while still in the 

 proventriculus, but it 

 can not act upon grains 

 and seeds until these 

 have been crushed in 

 the gizzard. Catarrh or inflammation of the mucous 

 membrane of the stomach is a not uncommon disease, 

 and one which seriously interferes with the vigor and 



Ostrich. 



Fig. 16.— Gastric plands of birds. 



