104 ANIMAL FUNCTIONS. 



Grinding apparatus of the Lobster. This part in the 

 Fig. 72. Lobster is represented by 



Fig. 72, which shows the 

 inside of the stomach, to- 

 gether with the triturating 

 machinery at its entrance. 

 There is a cartilaginous 

 frame work, in which the 

 hard calcareous bodies 

 marked a, b, and c, are 

 implanted. These have 

 the form, and perform the 

 office of teeth. The tooth , is situated in the middle 

 of this frame ; it has a conical rounded shape, and is 

 smaller than the others, b and c, are of the same size 

 and shape. 



When these three teeth are brought together by the 

 action of the surrounding muscles, they exactly fit into 

 each other, and are capable by the motion which is given 

 them, of completely pulverizing the small shells of 

 mollusca, which have been introduced into the cavity of 

 the stomach as food. 



Grinding apparatus of Birds. But the internal 

 machinery for grinding is larger, and more completely 

 formed in the granivorous, or grain-eating birds than 

 in any other animal. In carnivorous birds, as the owl 

 and eagle, this part is entirely wanting, but is found in 

 all the tribes which live on the seeds of vegetables as the 

 Hen, Goose, Pigeon, Swan, <fcc. In proper with the 

 ancient notion, that "every part helps a part," the grind- 

 ing faces of the gizzard are dried, ground, and taken to 

 help digestion, to this day. 



This organ, called the gizzard, has in its structure and 

 mode of action some analogy to the corn-mill. It con- 

 sists of two powerful muscles of a hemispherical shape 

 with their flat sides applied to each other, and their edges 

 united by a strong tendon which leaves an oval, vacant 



Describe the triturating machine in the stomach of the lobster. What 

 tribes of birds are furnished with gizzards 1 



, 



