154 



TEETH. 



Then, the grinding surfaces of the molars are no longer even or straight. 

 Comminution of an artificially -prepared diet, continued for a number of 

 years, seems to have worn the organs of mastication into a shallow and 

 eccentric curve; or, as pressure persevered with upon any living sub- 

 stance promotes absorption, probably the constant grinding of hardened 

 food has caused parts of the once even surface to be removed. 



THE JAW OP A FIVE-TEAE OLD. 



However, many readers may feel disposed to turn from the next illus- 

 tration, feeling their dislike of the image to be justified by denominating 



JAW OF A THIRTT-TEAR OLD. 



it an extreme instance. As such it is adduced, and no wrong is, there- 

 fore, done by so regarding it. It was inserted simply as bearing con- 

 spicuous evidence of that fact which it was the desire to establish. Few, 



