CHAEACTERISTICS OF BIKDS. 



119 



effectual by sand and small stones, which the Bird swal- 

 lows with its food. In Fig. 99 you see the gizzard of a 

 Turkey cut open. You observe the two semi-globular 



a 



Fig. 99. Gizzard of the Turkey. 



masses of muscle, and the lining covering them on the 

 inside of the organ. While these grind the food, the 

 gastric juice which digests it is all the time trickling 

 down upon it from the gullet at a, where it oozes out 

 from a great many little openings. 



203. This grinding operation of the gizzard takes the 

 place of the mastication which is done by those animals 



