160 



THE VITAL FUNCTIONS. 



from the mouth to a considerable distance under 

 the trunk of the body. 



Analogous in design to these pouches are the 

 dilatations of the oesophagus of birds, denominated 

 crops. In most birds which feed on grain, the crop 

 is a capacious globular sac, placed in front of the 

 throat, and resting on the furcular bone. The crop 

 of the Parrot is represented at c, Fig. 299 ; where, 



also, s indicates the cardiac 

 portion of the stomach, and 

 G the gizzard, of that bird. 

 The inner coat of the crop 

 is furnished with numerous 

 glands, supplying consider- 

 able quantities of fluid for 

 macerating and softening the 

 dry and hard texture of the 

 grain, which, for that pur- 

 pose, remains there for a con- 

 siderable time. Many birds feed their young from 

 the contents of the crop ; and, at those seasons, its 

 glands are much enlarged, and very active in pre- 

 paring their peculiar secretions : this is remarkably 

 the case in the Pigeon, which, instead of a single 

 sac, is provided with two, (seen at c, c, Fig. 300), 

 one on each side of the oesophagus (o). The 

 pouting pigeon has the faculty of filling these cavi- 

 ties with air ; producing that distended appearance 

 of the throat from which it derives its name. Birds 

 of prey have, in general, very small crops, their 

 food not requiring any previous softening; but the 

 Vulture, which gorges large quantities of flesh at a 

 single meal, has a crop of considerable size, forming, 

 w hen filled, a visible projection in front of the chest. 



