Memoir upon living and fossil Elephants. 59 



ever, evince something" much stronger in point of sensi- 

 bility. 



The txostoses of the teeth (their fimgositiei) do not grow 

 upon ihe surface of the enamel of a sound toolh, but iu the 

 bottom ot the hollows of the carious ones. These are p-o- 

 ductions of the pulpy nucleus, which have pierced the hard 

 matter in the thin bottom of these hollows. 



The continual lengthening of those teeth which have none 

 opposite to them to retain them, agrees with all these facts; 

 the portion once sent out of the tusk of the elephant length- 

 ens always, but does not become thicker, and does not har- 

 den : this is because it is always pushed back by new layers, 

 while in itself it cannot undergo any change. We know- 

 how lar this lenoftheniiTg proceeds in rabbits which have lost 

 a tooth, and whose opposite tooth is no longer worn by n)as- 

 tication. Continuing to lengthen backward, it finally Inn- 

 ders the animal from eating. It was from this that Aristotle 

 asserted that the teeth grow all our lives, while the other 

 bones have determinate limits. 



It must be added, however, that the ordinary teeth have 

 a determined limit: this is when the entrance of their ca- 

 vity is obliterated, and when their pulpy nucleus receives no 

 more nourishment ; but nature lias taken care to leave the 

 paths always open in those animals which, from wearing 

 their teeth much, require that they should be often repaired, 

 belimd : such are the rabbits with respect to their incisors, 

 and the elephants with respect to their tusks : the root ntver 

 being obliterated, its channel can never be closed. 



Article IV. 

 Application of the Observations upon ike Dentition of the 

 Elephant to the Knowledge of Fossils. 

 For want of information on the subject of the formatioa 

 and the manner in which teeth grow in general, descnbers 

 of fossils have committed a multitude of eirors; but as the 

 circumstances relative to the teeth of the elephant are still 

 more complicated and more difiicult than those which con- 

 cern the other animals, these have led people into much 

 greater mistakes. 



Formeily 



