330 STRUCTUEE AND ADAPTATION OF TEETH 



elongated. In some instances the tooth describes 

 a complete circle, the cutting apex even entering 

 the hollow cavity of the formative pulp ; and many 

 an unfortunate hare, which has survived for a 

 time the injuries received by a charge of shot, is 

 doomed to intense suffering and a lingering death 

 by starvation, resulting from the unnatural growth 

 of the long incisor teeth. 



In the family Leporidae, including rabbits and 

 hares, we have the only example of a second pair 

 of incisors, and these in the upper jaw only. 

 Instead of being situated laterally, as in other 

 animals, these incisors, which are of small dimen- 

 sions, are placed immediately behind the frontal 

 pair, serving as a kind of anvil to receive the 

 concussion of the lower teeth. 



An example is seen, in the capybara, of great 

 perfection in the molar teeth of a rodent, and of 

 the apparatus provided for their efficient employ- 

 ment. 



In the ruminants we observed that the crescentic 

 folds of the enamel were arranged longitudinally, 

 or in the same axis as that of the jaws, in accord- 

 ance with the motion from side to side in mas- 

 tication. 



There is a great difference in the complexity 

 of structure, and in the reproductive power 

 bestowed on the teeth of the various genera of 

 rodents. 



In the rats, which are omnivorous, the molar 



