1 INTRODUCTION. 



But the vascularity of the dentinal pulp, and, especially, the 

 rich network of looped capillaries that adorns the formative peri- 

 pheral layer at the period of its functional activity, have attracted 



Purkinje on the texture of dentine, which show that, if the pulp was converted at all, it must 

 be into a very diflferent tissue from bone, and consequently by a different process from 

 ossification. 



The nature of the process not having been discovered at that period, the formation of 

 dentine is described to be "by the secretion of layers of dental substance," and the shell of 

 osseous substance so formed, is said to have " no organic connection with the matrix ; it is 

 formed by the deposition of the mineral components of the tooth mixed with some animal 

 matter, and may be lifted off its matrix," (pp. 391 & 392). 



So also Prof, de Blainville, in the fasciculus of his great work " Osteographie d'Animaux 

 Vertebres," submitted by him to the French Academy, on the same day on which I 

 communicated to that learned body, my " Theory of the development of dentine by centripetal 

 calcification of the pulp," (December 16, 1839. See the ' Compte Rendu' of the Seance of 

 that day), says : " Pour bien comprendre la forme generale d'un phaneros," (by this name the 

 Professor designates the class of organs called * teeth') il faut savoir que c'est une partie morte 

 et produite, exhalee a la surface d'un bulbe producteur ou phanere, en continuite organique 

 avec le corps animal ; et implantee plus ou moins profondement dans le derme et meme dans 

 les tissus sous-jacents ; et que, par consequent, la forme du bulbe producteur determine 

 rigoureusement celle du produit on du phaneros. Or, par la production seule des couches 

 de celui-ci appliquees successivement, en dedans les unes des autres, sur le bulbe producteur 

 seul vivant, seul lie par le systeme vasculaire et par le systeme nerveux au reste de 

 I'organisme, ce bulbe dirainue de volume en meme temps que de puissance productrice ; en 

 sorte qu'il arrive un moment ou les cones composants, ayant cesse de s'accroitre en diametre 

 avec le bulbe lui-meme, commencent a dirainuer avec lui." — Fascicule Premier, Primates, p. 15. 



These formal expressions of well weighed ideas of the nature and formation of teeth, set 

 forth by the celebrated Professors of Berlin and Paris, afford the true indications of the state 

 and the needs of that branch of physiology at the close of the year 1839- By only one writer 

 had the casual expression by Dr. Schwann, in his general Treatise on the Correspondance 

 between Animals and Plants in their structure and development, of his leaning towards the 

 old and exploded opinion, that the dental substance is the ossified pulp, been cited prior to 

 that date, in reference to the question of dental development. It occurs in the full Report of 

 the communications by Mr. Nasmyth ^o the ' British Association' at Birmingham, in August, 

 1839, in the 'Literary Gazette' of September 21st, 1839; and, as these 'Communications' 

 betray a full knowledge of all that Schwann luul published relative to the development of 



