IN THE LOWER ANIMALS, ETC. 319 



on the grinding surface, while the dentine, and 

 especially the cement are more rapidly worn away, 

 a structure admirably adapted for bruising and 

 comminuting the woody fibre, and other hard 

 substances which constitute the elephant's food. 

 The molar teeth progressively increase in size and 

 the number of constituent plates ; the first molar 

 consisting of four plates, and the sixth of about 

 twenty-five. 



From the peculiar mode of dentition, the front 

 portion of a tooth has cut the gum, and is em- 

 ployed in mastication before the back part is com- 

 pletely formed, even before some of the posterior 

 denticles have been consolidated ; and the back 

 part of the tooth does not come into use until the 

 anterior portion has been worn down nearly to the 

 fang. When at length the complex molar has 

 become useless for grinding, the roots are ab- 

 sorbed, and, aided by the pressure of the succeed- 

 ing tooth, it is finally shed. It may therefore be 

 said that the elephant cuts a series of sets of teeth, 

 as the old ones are worn out ; an arrangement 

 which might be considered very convenient by 

 many members of the human family. 



In the Indian elephant, the grinding surfaces 

 of the dental plates represent flattened ovals 

 placed across the tooth ; but in the African spe- 

 cies these columns form in section a series of 

 lozenges, touching each other along the centre of 

 the tooth. 



