OF LIVING ELEPHANTS. 207 



rus^ the texture of which is naturally close, have often been given for 

 diseased ivory. There are some described under this title in Dauben- 

 ton himself. 



Diseases of the teeth are nearly in the same case as those of ivory. 



What has been called caries, an almost necessary consequence of 

 the removal of the enamel, is the decomposition which the internal 

 substance would undergo, when it would be no longer adherent to the 

 body, if it remained exposed to the heat of the mouth and to the ac- 

 tion of the saliva, and of the different aliments ; but it has no resem- 

 blance to caries of the bones. 



The liability of some persons to have their teeth become carious 

 arises from their substance not being of a good com23osition, and is 

 owing to the bad state of the pulpy nucleus when it transuded through 

 them. 



The same may be said of the spots and softer layers observed in the 

 substance of certain teeth. These are temporary affections of the 

 pulpy nucleus. 



Pains and inflammations are in the pulpy nucleus and not in the hard 

 part of the tooth. It is the pulpy nucleus which is sensible to shocks, 

 and to the temperature of bodies, through the envelope which the hard 

 part forms for it. 



One will be surprised, perhaps, that an envelope so thick and so 

 hard does not deaden all sensation; but the pulp of the nucleus of the 

 teeth is, next to the retina and the pulp of the labyrinth of the ear, the 

 most sensible part of the animal body. Fishes, which have their laby- 

 rinth shut in the cranium, without tympanum or small bones, in a 

 word, without any communication open externally, hear by means of 

 shoes communicated to the cranium ; this is something much stronger 

 in sensibility than what the teeth experience. 



The exostoses of the teeth, and fungous growths, do not at all come 

 to the surface of the enamel of the sound tooth, but in the cavities of 

 the caries. They are productions of the pulpy nucleus, which have 

 pierced the hard substance in the thinned fundus of these cavities. 



The continued lengthening of the teeth, which have none opposite 

 them to detain them, agrees with all these facts ; the portion of the 

 elephant's tusk once out is constantly lengthening", but not becoming 

 thicker, nor is it hardening ; it is because it is always pushed poste- 

 riorly by new layers, whilst itself cannot undergo any change. We 

 knoAV how far this prolongation is carried in rabbits which have lost a 

 tooth, and whose opposite tooth is no longer used in mastication. 

 Continuing to lengthen behind, it ends by preventing the animal from 

 eating. It is in this sense that Aristotle said, that the teeth grow 

 during the entire of life, whilst the other bones have determinate 

 limits. 



We must add, however, that the ordinary teeth also have a limit ; 

 it is when the entrance of their cavity is obliterated, and their pulpy 

 nucleus no longer receives nourishment ; but nature has taken care to 

 leave passages always open in animals, which, making frequent use of 

 their teeth, required to have them constantly repaired j^osteriorly : such 

 are rabbits for their incisive teeth, and elephants for tsheir tusks : the 

 root not becoming narrower in these, its canal cannot bsS closed. 



