HUXLEY, ON THE ENAMEL OF THE TEETH. 127 



tougher and more easily reduced to thin sections than other 

 coals. 



The differences it presents from other coals are, therefore, 

 non-essential ; not differences in kind, but in degree. The 

 Torbanehill coal differs from other gas coals in being the best 

 gas coal ; it differs from other cannel coals in being the best 

 cannel. 



On the Enamel and Dentine of the Teeth. By T. H. 

 Huxley, F.'R.S. 



The first part of the sixth volume of Siebold and Kolliker's 

 ' Zeitschrift fiir Wissenschaftliche Zoologie,' published in 

 July of the present year, contains a paper by M. Edouard 

 Lent, ' On the Development of the Dentine and Enamel of 

 the Teeth.' It could only be a source of gratification to me 

 that any one should have been led fairly to investigate a sub- 

 ject, by the perusal of a paper of mine published in this 

 Journal, even if his results were totally opposed to those at 

 which I had arrived ; and I do not think that, as a general 

 rule, controversial writing is worth the paper it is printed on 

 — assuredly, it is not worth the time it wastes. I should, 

 therefore, have had nothing to reply to M. Lent's unfavourable 

 expressions with regard to my labours, were it not for two 

 circumstances. In the first place, M. Lent is a pupil of Pro- 

 fessor Kolliker's, and appears to have worked under the eye 

 of that distinguished investigator. Indeed, the paper is so 

 completely sanctioned by Professor Kolliker, that I must regard 

 him as responsible for it. And in the second place, owing, 

 as I suppose, to M. Lent's inexperience as an author (though 

 truly the superintendence of so practised a writer as Pro- 

 fessor Kolliker should have obviated this difficulty), his 

 paper is curiously inconsistent with itself, being in form a 

 severe criticism and refutation — but, in fact, a confirmation 

 — of the views I ventured to promulgate. 



My paper was intended to establish two main points — 

 1. That there is no evidence that the dentine is formed by 

 direct conversion of pre-existing elements of the pulp. 2. That 

 the enamel is not developed externally to the so-called base- 

 ment membrane, or membrana preformativa of the pulp, but 

 internally to it ; Nasmyth's membrane, which lies over the 

 enamel, being in fact continuous with the membrana pre- 

 formativa. 



1. On this head, M. Lent adds no new fact or argument of 

 any kind. He simply repeats and confirms the statement 

 already made by Professor Kolliker — that minute gelatinous 



