872 



TEETH. 



masses with a grinding surface more like that 

 of the compound molars of the elephant. 



When a vertical and longitudinal section 

 is made of one of these upper pharyngeal 

 compound teeth, each denticle is seen to be 

 composed, as in fig. 558., of a body of very 

 hard and unvascular dentine d, with a thick 

 sheath of enamel e, the denticles being united 

 together by the cement c, and supported and 

 further united together, and to the pharyngeal 

 bone, by a basal mass of vascular osteo-dentine. 



Such are some of the prominent features 

 of a field of observation which comparative 

 anatomy opens out to our view ; such the 

 varied "nature, and such the gradation of 

 complexity of the dental tissues, which, up to 

 December 1839*, continued, notwithstanding 

 successive approximations to the truth, to be 

 described in systematic works as a " pha- 

 neros," or " a dead part or product exhaled 

 from the surface of a formative bulb I " The 

 truth may be slowly but is surely established, 

 subject to the usual attempts to mask or 

 detract from the merit of the discovery. By 

 no systematic authors has the hypothesis of 

 the formation of dentine by transudation or 

 secretion been more frequently or more ex- 

 plicitly enunciated than by the Cuviers. 

 Baron Cuvier repeats, in both editions of his 

 elaborate work the " Ossemens Fossiles " 

 " C'est dans ce vide conpevable que se de- 

 poseront les matieres qui doivent former la 

 dent, savoir : la substance vulgairement ap- 

 pelee osseuse, qui sera transudee par des pro- 

 ductions gelatineuses venant du fond de la 

 capsule, et 1'email qui sera depose par les 

 cloisons membraneuses," t.ii. p. 61., ed. 1812.; 

 t. i. p. 33., ed. 1821. See, also, M. F. Cuvier, 

 " Dents de Mammiferes," 8vo, 1825. " L'ivoire 

 se depose par couches concentriques," p. 

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

 contraire a 1'ivoire," ib. p. xxviii. And Baron 

 Cuvier again, in the second edition of his 

 "Leons d' Anatomic Comparee," t. iv. 1836, 

 p. 214 : "L'ivoire se depose par couches, par 

 une sorte de transudation." In the first 

 edition of this classical work, Cuvier had 

 illustrated the peculiarity of the teeth of 

 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 Squalei, 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 

 work, " Oste'ographie et Odontographie d'Animaux 

 Verte'bre's," which he submitted to the Academy of 

 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 

 of the cells of the pulp." 



osseous tissue of the epiphyses of bones was 

 developed differently from osseous tissue in 

 general, e. g. by the uniform and simultaneous 

 hardening or calcification, obscurely referred 

 to in the above quotation, may be questioned, 

 for such is not the way in which the teeth of 

 the shark are calcified. But this is certain, 

 that the idea, whatever it might have been, 

 had no influence on the fixed belief of the 

 developernent of the dental tissue by trans- 

 udation expressed in their later and more 

 elaborate works by Baron Cuvier and his ac- 

 complished brother ; and, in point of fact, the 

 passage which I have quoted is expunged from 

 the second edition of the " Leons d' Anatomic 

 Comparee," 1835 : the successive stages of 

 calcification in the different teeth of the same 

 vertical series in the jaw of the shark, having 

 probably been noticed in the interim by Cuvier. 

 The author of the article " Secretions " in 

 the " Dictionnaire Universel d'Histoire Na- 

 turelle," has, however, reproduced Cuvier's ob- 

 scure comparison of certain fishes' teeth to 

 the epiphyses of bone, as evidence of the need- 

 lessness of any ulterior researches for the 

 demonstration of the theory of dental de- 

 velopement by conversion and calcification of 

 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 

 such mode of developement of dentine : " En 

 1840 et 1841 (the * Comptes Rendus del'Acad. 

 des Sciences' give the true date) 1'etude des 

 dents de Squale par M. R. Owen, lui a de- 

 montree leur accroissernent par intussuscep- 

 tion, comme elle avait ete a G. Cuvier trente- 

 cinq annees auparavant." How or why G. 

 Cuvier came to abandon the theory so demon- 

 strated, and how it happened that none of his 

 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 : " Malheure'use- 

 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 

 and seeming contradiction to the theory of 

 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, 

 1846, 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 

 epiphyses of long bones. " L'ivoire se depose 

 par couches, par une sorte de transudation." 

 Le9ons d'Anat. Comparee, t. iv., 1836, p. 214. 

 To which proposition Cuvier has himself 

 added a note : " Je me suis assure recemment, 

 sur des germes de dents d'elephant, cjue la 

 substance osseuse de la dent se forme comme 



