HUMAN DENTITION. 451 



with its convexity next'the enamel: from ten to twelve dentinal tubes on 

 the same plane are included in the diameter of a peripheral calcige- 

 rous cell: the cells decrease in size and increase in number, and 

 become less definable as they become situated nearer the pulp-cavity. 

 The enamel fibres(l) are more wavy, even, than in the human teeth : 

 they are g^th of an inch in thickness, and manifest the striated 

 indication of their cellular origin as distinctly as in the human 

 teeth. The vertical fibres ascending from the summit of the crown 

 of the canine of the Chimpanzee described twenty acute-angled 

 undulations in their course. In the section examined, the bend 

 in one direction transmitted more light than in the opposite, and 

 gave an appearance of waves upon the cut surface of the enamel. 

 This is the character attempted to be shown by Fraenkel in fig. 4, 

 of his Thesis, and which Retzius says he had not succeeded in 

 observing in human enamel. The lines of growth or strata of the 

 enamel were best displayed in transverse sections of the incisors and 

 canines. The cement is thickest at the apex of the fang ; the Pur- 

 kingian cells are traceable to near the neck of the tooth, over which 

 the clear basis of the cement is continued upon the enamel : the tubuli 

 continued from the cells are most numerous on the side next the 

 dentine: they form likewise rich anastomotic plexuses in the in- 

 terspaces of the cells, besides communicating with peripheral ra- 

 mifications of the tubuU of the dentine: their diameter is Jj^;t\\ 

 of an inch. 



CHAPTER X. 



TEETH OF BIMANA. 



173. Having reached in the Chimpanzee the highest step in 

 the series of the brute creation, our succeeding survey of the Human 

 dental system, expanded by retrospective comparisons, becomes 

 fraught with pecuUar interest, since every difference so detected 

 establishes the true and essential characteristics of that part of 

 Man's frame. 



(1) PI. 119 a, fig. 1 e, e. 



G G 2 



