280 NATURAL THEOLOGY. 



ed* a circumstantial resemblance between the 

 stomachs of gallinaceous fowls and the structure 

 oi corn-mills. Whilst the two sides of the gizzard 

 perform the office of the mill-stones, the craw or 

 crop supplies the place of the liopper. 



When om' fowls are abundantly supplied with 

 meat, they soon fill their craw ; but it does not 

 immediately pass thence into the gizzard ; it al- 

 ways enters in very small quantities, in proportion 

 to the progress of trituration, in like manner as, 

 in a mill, a receiver is fixed above the two large 

 stones, which serve for grinding the corn, which 

 receiver, although the corn be pnt into it in bush- 

 els, allow the grain to dribble only in small quan- 

 tities into the central hole in the upper mill-stone. 



But we have not done with the alimentary his- 

 tory. There subsists a general relation between 

 the external organs of an animal by which it pro- 

 cures its food and the internal powers by wiiich 

 it digests it. Birds of prey, by their talons and 

 beaks, are qualified to seize and devour many spe- 

 cies both of other birds and of quadrupeds. The 

 constitution of the stomach agrees exactly with 

 the form of the members. The gastric juice of a 

 bird of prey, of an owl, a falcon, or a kite, acts 

 upon the animal fibre alone ; it will not act upon 

 seeds or grasses at all. On the other hand, the 

 conformation of the mouth of the sheep or the 

 ox is suited for browsing upon herbage. Nothing 



+ Disc. i. sec. liv. 



