314 POULTRY PRODUCTION 



The Digestive Tract. — "The structure of the ahmentary 

 canal of the bird suggests that the digestive process is rapid 

 and that it partakes of features associated with both the 

 carnivora and herbivora. Thus the relative shortness in 

 length is a carnivorous characteristic, while the character 

 of the diet and the thorough comminution of the food in the 

 gizzard are features more akin to the herbivorous type."^ 



Mouth Parts? — ^The distinctive character of the mouth 

 of birds is the absence of lips and teeth, these parts being 

 replaced by a horny mandible on each jaw and forming the 

 beak of the land fowl and the bill of the water fowl. With 

 land fowl the beak is short, pointed, thick and strong, the 

 upper mandible curving over the lower. In water fowl the 

 bill is longer, less firm, flatter, widened at its outer end, and 

 supplied along the edges of each mandible and within the 

 mouth with a series of thin and sharp transverse laminae, 

 whose purpose is to cut soft herbage. 



The tongue in fowls and turkeys is shaped like the barbed 

 head of an arrow with the point directed forward. The 

 barb-like projections at the back of the tongue serve the 

 purpose of forcing the grain toward the entrance to the gullet 

 when the tongue is moved from front to back. In water 

 fowl, the tongue is wider, softer, and more flexible. 



The salivary glands are present in the mouth of the com- 

 mon sorts of domestic birds, but are imperfectly developed. 

 Shaw' recently showed that ptyalin, a starch-digesting 

 enzyme, is present in the saliva of a chick soon after hatch- 

 ing. The presence of abundant saliva is made unnecessary 

 by the fact that the feed is swallowed whole, or in quite 

 large pieces, and there is little opportunity for its action. 



Gullet and Crop. — Upon leaving the mouth the feed is 

 forced into the gullet by the tongue. The gullet (esophageal 

 canal) is distinguished by its enormous expansibility. 

 Immediately before entering the body cavity the' gullet 



' Brown, Bureau of Animal Industry, Bulletin No. 56. 



' This account of the digestive tract is gleaned from various sources, 

 principally McNair, New York State Veterinary College Laboratory 

 Bulletin No. 3, Chaveauxs' Comparative Anatomy of Domesticated 

 Animals, and F. Smith's Manual of Veterinary Physiology. 



' American Journal of Physiology, 1913, vol. xxxi, No. 7. 



