872 



TEETH. 



masses with a grinding surface more like that osseous tissue of the epiphyses of bones was 

 of the compound molars of the elephant. developed differently from osseous tissue in 



When a vertical and longitudinal section general, e. g. by the uniform and simultaneous 

 is made of one of these upper pharyngeal hardening or calcification, obscurely referred 

 compound teeth, each denticle is seen to be to in the above quotation, may be questioned, 

 composed, as in Jig. 558., of a body of very for such is not the way in which the teeth of 

 hard and unvascular dentine d, with a thick the shark are calcified. But this is certain, 

 sheath of enamel e, the denticles being united that the idea, whatever it might have been, 

 together by the cement c, and supported and had no influence on the fixed belief of the 

 further united together, and to the pharyngeal developement of the dental tissue by trans- 

 bone, by a basal mass of vascular osteo-dentine. ndation expressed in their later and more 



elaborate works by Baron Cuvier and his ac- 



Snch are some of the prominent features complished brother ; and, in point of fact, the 

 of a field of observation which comparative passage which I have quoted is expunged from 

 anatomy opens out to our view ; such the the second edition of the " Lecons d' Anatomic 

 varied 'nature, and such the gradation of Comparee," 1835 : the successive stages of 

 complexity of the dental tissues, which, up to calcification in the different teeth of the same 

 December 1839*, continued, notwithstanding vertical series in the jaw of the shark, having 

 successive approximations to the truth, to be probably been noticed in the interim by Cuvier. 

 described in systematic works as a " pha- The author of the article " Secretions "in 

 neros," or " a dead part or product exhaled the "Dictionnaire Universel d'Histoire Na- 

 from the surface of a formative bulb ! " The turelle," has, however, reproduced Cuvier's ob- 

 truth may be slowly but is surely established, scure comparison of certain fishes' teeth to 

 subject to the usual attempts to mask or the epiphyses of bone, as evidence of the need- 

 detract from the merit of the discovery. By lessness of any ulterior researches for the 

 no systematic authors has the hypothesis of demonstration of the theory of dental de- 

 the formation of dentine by transudation or velopement by conversion and calcification of 

 secretion been more frequently or more ex- the pulp. The passage from the third vol. 



of the old edition (1800) of the " Lecons 

 d'Anat. Comp.," p. 112, is cited to show that 

 it naturally conducts to the knowledge of 



plicitly enunciated than by the Cuviers. 

 Baron Cuvier repeats, in both editions of his 

 elaborate work the " Ossemens Fossiles " 



" C'est dans ce vide conp evable que se de- such mode of developement of dentine : 

 poseront les matieres qui doivent former la 1840 et 184-1 (the 'Comptes Rendus del' Acad. 

 dent, savoir : la substance vulgairement ap- des Sciences' give the true date) 1'etude des 

 pelee osscuse, qui sera transudee par des pro- dents de Squale par M. R. Owen, lui a de- 

 ductions gelatineuses venant du fond de la montree leur accroissement par intussuscep- 

 ' capsule, et 1'email qui sera depose par les tion, comme elle avail etc a G. Cuvier trente- 

 cloisons membraneuses," t. ii. p. 61., ed. 1812.; cinq annees auparavant." How or why G. 

 t. i. p. 33., ed. 1821. See, also, M. F. Cuvier, Cuvier came to abandon the theory so demon- 

 " Dents de Mammiferes," 8vo, 1825. " L'ivoire strated, and how it happened that none of his 



En 



se depose par couches concentriques," p 

 xxvii. ; " L' email se depose dans un sens 

 contraire a Pivoire," ib. p. xxviii. And Baron 

 Cuvier again, in the second edition of his 

 "Lecons d'Anatomie Comparee/' t. iv. 1836, 



contemporaries adopted it, M. Duvernoy does 

 not explain. He does give a reason for the 

 omission, in the second edition of the " Lecons 

 d'Anat. Comp." of the passage which he affirms 

 to contain the demonstration : " Malheureuse- 



p. 214- : "L'ivoire se depose par couches, par ment, le copiste de cet ancien texte pour la 



2de edition a omis ce passage, par oubli." It 

 was natural to conclude that its obscurity 



illustrated the peculiarity of the teeth of and seeming contradiction to the theory of 



une sorte de transudation." In the first 

 edition of this classical work, Cuvier had 



certain fishes, which are at first detached and 

 afterwards united to the jaw-bone, by com- 

 paring their growth to that of the epiphyses 

 of the long bones : " Mais les dents qui ne 

 tiennent qu'a la gencive seulement, comme 

 celle des Squalci;, croissent a la maniere des 

 epiphyses des os, c'est-a-dire que toute leur 

 substance osseuse est d'abord tendre et po- 

 reuse, et qu'elle se durcit uniformement, et 

 finit par devenir entierement dure comme de 

 1'ivoire," t. iii. 1805, p. 112. Whether the 

 great anatomist meant to imply that the 



See the Fasciculus of M. de Blainville's great 



dental developement, formally propounded by 

 Cuvier, as well as to the facts shown by 

 nature in the sharks, had been the cause of 

 its omission ; but even had the misfortune 

 to which M. Duvernoy now attributes that 

 omission (for in the copious list of addenda 

 and corrigenda to the fifth, 1837, and final, 

 1816, volumes it is not noticed) not occurred, 

 the coincidence of such passages as the fol- 

 lowing would still have been inexplicable 

 and irreconcilable with the deductions that 

 M. Dumeril is now enabled to draw from the 

 comparison of the shark's tooth with the 



OCC LJL1C -I- <lO_i^li.lU.O V'l J.A. U.G JLIlclll 1C O tlCclU . ' _ - t T 9" * J ' 



work, " Oste'ographie et Odontographie d'Animaux epiphyses of long bones. L ivoire se depose 

 Vertebre's," which he submitted to the Academy of par couches, par une sorte de transudation. ' 



Sciences of the Institute of France on the same day, 



December 16th, 1839, on which I communicated, on 



the occasion of my election as corresponding member 



of that body, my " Theory of the development of ,. , . 



dentine by centripetal calcification and conversion sur des germes de dents d elephant, que la 



Lecons d'Anat. Comparee, t. iv., 1836, p. 214. 

 To which proposition Cuvier lias himself 

 added a note : " Je me suis assure recemment, 



of the cells of the pulp." 



substance osseuse de la dent se forme comme 



