128 HUXLEY, ON THE ENAMEL 



processes may often be found passing from the surface of the 

 pulp into the dentinal canals (a statement which no one de- 

 nies), and then takes for granted Professor Kolliker's purely 

 hypothetical interpretation of this fact — i. e., that these pro- 

 cesses are outgrowths of the " cells" of the surface of the pulp 

 — an hypothesis which is not supported, so far as I am aware, 

 by a shadow of direct evidence ; and it is to be remembered 

 that the fact is as well accounted for by my hypothesis as by 

 any other. 



So much for the formation of the dentinal tubules. With 

 regard to the substance of the dentine, M. Lent does not seem 

 to have seen much more than myself; for he says that " it is 

 more probable — indeed certain" that the " grund-substanz " 

 is an ^^ excretion of the cells and their processes."" (p. 127.) 



That is to say, M. Lent {i. e. Professor Kolliker) admits 

 that there is no new evidence to be brought forward as to the 

 formation of the dentine tubules, and that the substance of 

 the dentine is formed as I have stated it to be. Truly, then, 

 I do not see where the " irrige ansicM' with which I am 

 charged lies. 



At page 128 there is a very careless misstatement, which 

 one might be disposed to overlook in a student, but which is 

 utterly unpardonable in a production which has the advantage 

 of Professor Kolliker's deliberate imprimatur. 



" As regards Huxley's erroneous view as to the formation of 

 the dentine, I will only briefly remark, that Huxley has been 

 so unfortunate as to have seen the dentine from above only." 

 (p. 128.) 



This is truly astounding, considering that at page 160 of my 

 paper I give particular directions how to obtain a profile view 

 of the dentine in undisturbed connexion with the pulp ; that 

 figs. 3 and 4 are careful representations of such profile views ; 

 and that I lay particular stress upon the advantages to be de- 

 rived from this mode of examination. 



2. With regard to the development of the enamel, M. Lent 

 {i. e. Professor Kolliker) affords a confirmation of my views ; 

 all the more valuable, as it is evidently most unwillingly 

 wrung from him. 



At page 129, M. Lent, after stating the ordinary theory of 

 the development of the enamel, says: "This simple theory 

 must, however, I believe, be given up, since Huxley has 

 made a discovery whose truth I must confirm — a discovery 

 which greatly enhances the difficulty of accounting for the 

 formation of the enamel." 



Again, at page 133 : " From what has been said, it is pretty 

 clear that the membrana preformativa, which may be detached 



