262 Memoir i/pon living and fossil Elephants. 



the enamel. The opinion of Hunter, that the enamel is only 

 the sediment of the liquid interposed between the tooth 

 and its capsule, is inaccurate, inasmuch as it keeps too far 

 6ut of view the capsular membrane, whence in reality the 

 molecules of the enamel issue ; but it is very true, that 

 these molecules are at first betw een this membrane and the 

 tooth, before glueing themselves to the latter. As to the other 

 opinion, which makes the enamel come out as if by efflo- 

 rescence from the pores of the osseous substance; although 

 it has been adopted by several anatomists, it has no found?.' 

 lion whatever. But to return to our teeth. 



A thick layer of enamel thus coating the corona on all 

 sides, fills a part of the intervals which the transversal la- 

 minre and their notches had at first left between them. 



The rest of these intervals is completely filled up by a third 

 substance, which Mr. Tenon has called osseous cortical, be- 

 cause it envelops all the others, and resembles a common 

 bone in its chemical nature and hardness, still more than 

 the two other parts of the tooth. Mr, Home calls it lin7iey 

 while he gives the name of ivory to the substance vulgarly 

 called osseous. Mr. Blake gives to this cortical substance 

 the name of crust a petrosa. 



There is something very remarkable in its production. Mr, 

 Tenon thought it proceeded from the ossification of the in- 

 ternal lamina of the capsule, after it has produced the ena- 

 mel. Mr, Blake thinks that this lamina, after having given 

 the enamel bv one of its faces, gives the cortical by its op- 

 posite face. Mr, Home docs not express himself clearly 

 upon this subject. 



For my part, T am convinced that the cortical is produced 

 by the same lamina, and the same face which has produced 

 the enamel : the proof of this is, that this lamina remains 

 outside of the cortical, as it was formerly outside of the ena- 

 mel, and that it remains there soft and free as long as this cor- 

 tical gives it room. It changes in its texture alone ; while it 

 was producing enamel only it was thin and transparent. In 

 order to produce cortical, it becomes thick, spongy, opaque 

 and reddish. The cortical when crowing; is not like threads, 

 it rather resembles small drops thrown out as if by chance. 



The 



