CLASS AVES (BIRDS). 



3 2 3 



of the neck and of the legs in birds. The student sttould 

 verify this by his own observations. The chief muscles 

 of the bird are those of the legs and of the breast. If 

 the muscles are much used they are dark; if little used 

 light, as in the breast of the turkey. Why? 



FIG. 131. Diagram of the stomach and oesophagus of the fowl, o, oesophagus; 

 c, crop; p, proventricules or glandular stomach; g, gizzard or grinding stomach; 

 i, intestine. 



Questions on the Figure. Compare this stomach \vith Fig. 147 

 in respect to complexity. What are the functions of the various 

 regions? Why is the crop located outside the cavity inclosed by 

 the ribs ? 



327. Food and Digestion. Birds eat more food in 

 proportion to their size than any other animals probably. 

 This is connected with their great activity and their high 

 temperature, which is even greater than that of the 

 mammals. Birds may live on fruits and berries, on 

 seeds and grains, on insects and other small animals, on 

 decaying flesh, or may capture living prey, as fish, rep- 

 tiles, frogs, or even other birds. Their beaks and claws 

 as well as the internal parts of the digestive organs vary 

 according to the nature of the food. Probably the most 

 striking internal difference is in the crop and the grinding 



