44 CAKTILAGE. BONE. TEETH. 



an amorphous substance is poured out in the intervals 

 between them, an exudation furnished, no doubt, by 

 the deeper cells of the germ, and which subsequently 

 becomes the fundamental substance of the ivory of 

 the tooth. Finally, its development is completed by 

 the infiltration of the fundamental substance with 

 calcareous salts, and what remains of the original 

 Development g erm becomes atrophied and forms the dental pulp. 

 The germ of the enamel, having attained its com- 

 plete development, envelopes entirely the base of the 

 germ of the ivory, which we have traced to its com- 

 plete ossification. Superficially it is made up of con- 

 necting tissue rich in blood-vessels ; more deeply 

 there are only star-shaped cells imbedded in amor- 

 phous material ; and finally the stratum immediately 

 in contact with the dental germ, is formed by an 

 epithelial layer, whose cells, long, narrow, and pris- 

 matic in shape, resemble closely the prisms, already 

 described, of the enamel. Thus it is more than pro- 

 bable that the enamel is formed directly by the 

 f petrifaction of these elementary bodies. The lower 

 partions of the dental sac give origin to the cemen- 

 tum, taking on the process of ossification in the same 

 manner as periosteum. 



In view of the fact that connecting tissue, under 

 certain circumstances, undergoes transformation into 

 cartilage and bone, as well as into the substance of 

 the teeth, these tissues, being all analogous in nature, 

 are grouped together, by some authorities, in one 

 family. 



The preparations required for the study of the 

 structure of the teeth are prepared in the same man- 

 ner a*s sections of bone. 



