RECEPTACLES FOR RETAINING FOOD. 



179 



Analogous in design to these pouches are 

 the dilatations of the oesophagus of birds, deno- 

 minated 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 repre- 

 sented at c, Fig. 29D; where, also, s indicates 



the cardiac portion of the 

 stomach, and g the giz- 

 zard, of that bird. The 

 inner coat of the crop is 

 furnished with numerous 

 glands, which pour out 

 considerable quantities of 

 fluid for macerating and 

 softening the dry and 

 hard texture of the grain, 

 which, for that purpose, 

 remains there for a considerable 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 preparing their 

 peculiar secretions : this is remarkably the case 

 in the Pigeon (Fig. 300), 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 cavities with air, which produces that dis- 

 tended appearance of the throat from which it 

 derives its name. Birds of prey have, in general, 



