exercises only a gentle stimuluis to the vital processes. 

 Cuvier believed that there were places where the dentinal 

 pulp and the capsule were separate from each other. I 

 have never found such, except where the enamel-pulp 

 was interposed between them in the crown of the tooth, 

 or where both pulp and capsule adhered to the periosteum 

 of the socket, below the crown. Cuvier afiirms that the 

 number of fangs of an elephant's molar depends upon 

 the number of points at which the base of the gelatinous 

 (dentinal) pulp is attached to the bottom of the capsule ; 

 and that the interspaces of these attachments constitute 

 the under part of the crown or body of the tooth, the 

 attachments themselves forming the first beginnings of 

 the fangs. True to his hypothesis of the formation of the 

 dental tissues by excretion, he says that the elongation 

 of the fangs is produced by two circumstances ; first, the 

 progressive elongation of the layers of osseous substance 

 (dentine) which force the tooth to rise and emerge from 

 its socket ; secondly, the thickening of the body of the 

 tooth by the addition of successive layers to its inner sur- 

 face, which, filling up the interior cavity, leaves scarcely 

 room for the gelatinous pulp, and forces it down into the 

 interior of the roots. ^ 



This pulling up of the fang on the one hand, and squeez- 

 ing down the pulp on the other, are forces too gross and 

 mechanical to be admitted in actual physiology to explain 

 the growth of the root of a tooth or of any other organized 

 product ; such modes of explanation were, however, in- 

 evitable in adopting the "excretion theory" of dental 

 development. 



There are few examples of organs that manifest a more 

 striking adaptation of a highly complex and beautiful 

 structure to the exigences of the animal endowed with it, 



