CHAPTER IV. 



THE DEVELOPMENT OF THE TEETH. 



THE development of the teeth is a process which, while 

 subject to modifications in the different groups of verte- 

 brates, retains nevertheless in all certain essential charac- 

 ters, so that it becomes possible to embody its main features 

 in a general account. 



Prior to the commencement of any calcification there is 

 always a special disposition of the soft tissues at the spot 

 where a tooth is destined to be formed ; and the name of 

 " tooth germ " is given to those portions of the soft tissue 

 which are thus specially arranged. All, or a part only, of 

 the soft structures making up a tooth germ, become con- 

 verted into the dental tissues by a deposition of salts of lime 

 within their own substance, so that an actual conversion of 

 &t least some portions of the tooth germ into tooth takes 

 place. The tooth is not secreted or excreted by the tooth 

 germ, but an actual metamorphosis of the latter takes 

 place. The details of this conversion can be better dis- 

 cussed at a later page ; for the present it will suffice to say 

 that the three principal tissues, namely, dentine, enamel, 

 and cementum are formed from distinct parts of the tooth 

 germ, and that we are hence accustomed to speak of the 

 enamel germ and the dentine germ ; the existence of a 

 special cement germ is asserted by Magitot, but as yet his 

 descriptions await confirmation. 



In many anatomical works which the student may have 

 occasion to consult, the process of tooth development may 



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