21 



cells or corpuscles of the crusta petrosa, though in 

 works of high authority, drawings obviously indi- 

 cating such a connexion, are presented ; they are 

 limited to the ivory, and terminate within it. What 

 their exact use may be, is not known, but that they 

 are of service, their presence is sufficient proof. Like 

 the minute canals of bone, they probably convey a 

 serous or colourless fluid, for the nutrition of the part 

 in which they are developed. 



The relative positions of the various structures that 

 enter into the composition of the incisor tooth, will be 



