INTRODUCTION. xli 



Observations on the pulp, in its various stages of conversion into 

 dentine, whilst in undisturbed connection with the calcified portion, 

 in the thin, transparent, lamelliform teeth of a fetal Shark {Carcharias) , 

 first yielded me unequivocal demonstration of the organic continuity 

 of the cap of dentine with the supporting vascular pulp ; they also 

 indicated some stages of the progress of the conversion of the pulp 

 into dentine, and produced that clear idea of the nature and relations 

 of dental development, which is expressed in the ' Theory of dentifi- 

 cation by centripetal calcification of the pulp's substance,' submitted 

 to the French Academy in December, 1839.(1) 



The following are the progressive steps of the calcifying pro- 

 cesses, according to my microscopic researches on the formation of 

 the different substances which compose the more complex teeth of 

 Reptiles and Mammals, pursued in various species of both classes, 

 but chiefly in the higher organized domestic animals. 



Three formative organs are developed, as already described, 

 for the three principal or normal dental tissues. The dentinal pulp 

 (PI. 122 a, figs. 5, 6, 7 k 8, d), or pulp proper, for the dentine ; the 

 ' capsule' (ib. c) for the cement, and the ' enamel-pulp' (ib. e) for 

 the enamel. The essential fundamental structure of each formative 

 organ is cellular; but the cells differ in each organ, and derive 

 their specific characters from the properties and metamorphoses of 

 their nucleus, upon which the specific microscopical characters of 

 the resulting calcified substances depend. 



Cl) The general results only of this communication were given in the ' Comptes Rendus,' 

 1839, p. 784. The Commission appointed by the French Academy to report on a subsequent 

 Memoir on the same subject advert to some of the phenomena previously communicated by me. 

 " Quant aux preparations qui montrent I'areolite de la pulpe, non seulement nous les avons 

 reproduites avec succes, mais de plus nous avons constate, a I'etat frais, la granulation 

 des areoles signalee par M. Richard Owen," loc. cit. 1842, p. 1063. 



d 



