VI. 



ON THE DEVELOPMENT OF THE ENAMEL IN 

 THE TEETH OF MAMMALS, 



AS ILLUSTRATED BY THE VARIOUS STAGES OF GROWTH DEMON- 

 STRABLE IN THE EVOLUTION OF THE FOURTH MOLAR OF A 

 YOUNG ELEPHANT, ELEPHAS INLICUS, AND OF THE INCISOR 



A naked-eye examination of a spirit preparation of a developing 

 molar tooth of an elephant appears to be sufficient to show that in 

 development the dentine takes precedence of the enamel in the tooth. 

 In such a tooth a certain number of the more anteriorly placed 

 denticles may be seen to be formed of caps of dentine, of a yellowish 

 colour, encrusted, for various distances from their apices downwards, 

 with opaque white deposits of enamel. Posteriorly to the denticles 

 of this composite character, we see a few denticles consisting of 

 dentine alone, upon which no deposition of enamel has as yet taken 

 place ; and, most posteriorly of all, we see processes of the dentinal 

 pulp, which, as yet, are devoid of any covering of dentine. 



*If, in the second place, we proceed to take note of the capsular 

 processes in which the denticles are enclosed, we shall observe that 

 the inner (reflected) surfaces of certain of these capsules are rough- 

 ened over by deposit, in correspondence with the enamel deposit 

 already noticed on the denticles which they surround. The deposit 

 on the inner surface of the capsule is soft, and consists of cylindri- 

 form cells packed closely together, and forming, when their interior 

 surface is looked down upon, a mosaic arrangement by their apposi- 

 tion, whilst in the immediate neighbourhood of their exterior (their 

 still attached) surface, numerous blood-vessels are seen ramifying. 

 There can be no doubt that we have here the often-described proxi- 

 mal, and, as yet, but imperfectly calcified ends of the enamel-cells, 



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