THE TEETH. 69 



nuclei of these cells, or are, and this at present appears to me 

 to be more probable, the remains of the cavities of the cells, 

 whose boundaries have undergone a greater consolidation, and 

 therefore correspond with osseous lacuna. The divisions of 

 the canals are explained, if we conceive, either that the den- 

 tinal cells divide longitudinally from time to time, as I be- 

 lieve I have actually observed, or that a cell coalesces with two 

 of its predecessors. As to the more delicate ramifications, we 

 can only suppose that they are formed by a secondary process 

 of resorption in already formed dentine, like that which must 

 be assumed to occur in the osseous lacuna, to account for the 

 anastomoses of their canaliculi, and their communication with 

 Haversian canals ; at least, I see no possibility, whatever view 

 we take, of explaining their formation in any other way, without 

 coming into opposition with well-ascertained facts. No such 

 process as the thickening and ossification of dentinal cells ac- 

 companied by the formation of pore-canals can be observed, so 

 that the fine lateral branches appear to be entirely of secondary 

 origin. 



In the course of the ossification of the dentine, at least in 

 man, we find that the deposition of calcareous salts in the recently 

 formed, structurally characterised, though only slightly hardened 

 dentine, takes place in such a manner thatthe whole appears to 

 consist of isolated globules. These globules, which are visible 

 not only at later periods, but in the earliest cap of dentine and 

 are best seen at the edge of the root of a large tooth viewed 

 externally, eventually disappear if development proceed nor- 

 mally, calcareous matter being deposited between them, so that 

 the dentine becomes quite homogeneous and clear; in the 

 opposite case, they persist in greater or less number, and 

 the spaces between them, which are nothing but the inter- 

 globular spaces above described, contain unossified dentine. 



According to my observations, the development of the cement 

 takes place from that portion of the dental sac which lies be- 

 tween the pulp and the enamel organ and commences, even 

 before the eruption of the teeth, contemporaneously with the 

 formation of their fangs. About this time the dental sac 

 elongates inferiorly, applies itself to the growing fang, yields, 

 from its abundant vascular network, a soft blastema, in which 

 nucleated cells are developed, and tr en ossification takes place. 



