19G ON THE FOSSIL BONES 01' PACHYDERMATOUS QUADRUPEDS. 



It is in this vacuum, which is very readily co.nceived, that the matters 

 \vhich are to form the tooth are to be deposited, to wit, the substance 

 commonly called osseovs, which is to transude through the gelatinous 

 productions coming from the bottom of the capsule, and the enamel, 

 which shall be deposited by the membranous partitions, and in general 

 by the entire inner surface of the capsule and its productions, the base 

 alone excepted*. 



: It must, however, be rem'arked, that between the osseous substance 

 and the enamel there is still a very fine membrane, which I think I have 

 discovered. When there has as yet no part of the first substance 

 transuded, this membrane immediately envelopes the small gelatinous 

 waU, and the serre very closely. 



In proportion as this small partition transudes through this substance, 

 it, as it were, shrinks and retires inwards and separates from the mem- 

 brane, which nevertheless always serves it as a tunic, but as a tunic com- 

 mon to it and to the substance which it has transuded under it. 



The enamel, again, is deposited on this tunic by the productions of the 

 internal lamella of the capsule, and it so presses it against the inner or 

 osseous substance, which it separates from it, that this tunic soon becomes 

 imperceptible in the hardened portions of the tooth, or at least that it 

 appears there only on cutting it, as a greyish very fine line, which sepa* 

 rates the enamel from the inner substance. But we then always see 

 that it is it only which attaches these hardened parts to the fundus of the 

 capsule ; for without it there would be a solution of continuity. 



The substance called osseous and the enamel are produced, then, by 

 a sort of jnxta position. 



The first is formed in layers from without inwards ; the inner layer 

 is that last formed, and it is also the most extended, precisely as ia 

 shells; and its formation commencing by the most prominent points 

 of the gelatinous nucleus of the tooth, it is on these points that this 

 substance is thickest : it continues diminishing in thickness, accord- 

 ing as it becomes more distant from them. 



Let us now carry back our thoughts to the period when this trans- 

 udation commences ; it may be readily conceived that there is formed 

 a small cup (calotte) on each of the dentuli, which divide the edges 

 of the small gelatinous partitions already so often mentioned. 



In proportion as new layers are added interiorly to the former, the 

 cups (calottes) are changed into conical horns (cornets) ; if the new 

 and inner layers descend to the bottom of the fissures of the edges of 

 these small partitions, all the horns unite into one single tranverse 

 lamella ; in fine, if they descend to the base of the small partitions 

 themselves, all the tranverse lamellae will be united into a single 

 crown of a tooth, which would present the same eminences and the 

 same undulations as were seen in the gelatinous nucleus, if, during the 

 time when these layers were transuding, other substances had not 

 been deposited above, and so filled up in part the intervals. 



At first the enamel is deposited, as I said, on the surface of the 



* See, for the production of the enamel, the Preliminary Discourse in the work of 

 M. F. Cuvier, entitled, Ses dents des Mammiferes considerees comme caracieres soolo- 

 giques, Sfc, 



