CIRCULATORY SYSTEM 



297 



follows: (1) The beak, or mandibles, for picking up feed and 

 sometimes cutting or tearing it; (2) the gullet, through which 

 feed passes, after being moistened in the mouth with saliva; (3) 

 the crop, or temporary receptacle; (4) the stomach (proventriculus), 

 where gastric juice is secreted and mixed with it; (5) the gizzard, 

 a strong muscular sac, where, by means of small stones and sharp 

 grit (serving as the teeth of the bird), the feed is ground more finely 

 than in the mouths of many 

 of the larger animals; and (6) 

 the intestine, a long tube which 

 receives the pulped material 

 from the gizzard, subjects it 

 to the action of several juices 

 from the pancreas, the liver, 

 and other glands, and absorbs 

 the digested and dissolved por- 

 tions; the undigested residue 

 passes along to (7) the cloaca, 

 where it mixes with the waste 

 materials from the genito-uri- 

 nary canal, which empties into 

 the intestine at this point. 



Circulatory System. — The 

 circulatory system of the fowl 

 is very similar to that of mam- 

 mals, being composed of a 

 heart with four cavities, from 

 which the blood is pumped to 

 all parts of the body, through 

 blood vessels, some of which 

 convey nourishment, while oth- 

 ers purify the body by carry- 

 ing away its waste material. 

 The blood of birds is about 

 two or three degrees warmer 

 than that of mammals. 



The circulatory system is composed of two distinct circuits or 

 courses which the blood takes in passing through the body. The 

 diagram (Fig. 143) shows the course of the blood. The heart is 

 designed to pump two streams of blood at once, its left side pump- 

 ing the blood through the body and the right side through the 



Fia. 143. — Circulatory system of the fowl. 



