INTRODUCTION. xlv 



uncalcitied surface of the pulp (fig. 3, b) presents the appearance 

 of a net-work, the meshes being formed by the exposed cells, and 

 the intervening very thin layer of blastema. Each mesh, however, 

 which gives a transparent or bright contour to the cell, when 

 viewed by transmitted light, instead of presenting a single stellate 

 nucleus, shows by well directed light under a higher power, several 

 points, each of which is the centre of one of the meshes of a 

 finer network : these points are the ends of the granular elongated 

 nuclei, (1) which have been torn from the cavities of the dentinal 

 tubes in the displaced cap of dentine. A piece of the thin trans- 

 parent margin of the cap of a growing tooth, which may be cut oft' 

 with a pair of fine scissors, easily affords the means of demonstrating 

 the corresponding structure in that calcified part of the pulp. A slight 

 change of focus is required to bring the ends of the tubuli in view, 

 from that in which the clear outline of the dentinal cell is best seen. 

 In proportion as the progress of calcification approximates the 

 cells, and as these have undergone the changes in their nucleolar 

 contents, preparatory to the proper arrangement of the hardening 

 salts within, the proportion of the basal substance in the inter- 

 spaces of the cells to the enlarged cells themselves decreases, and 

 the cells become more readily detached and seemingly independent, 

 when torn out in the displacement of the cap of dentine. Although 

 they are less adherent laterally to the basal substance of the pulp, 

 they are more coherent with the cells of the same linear series : the 

 tubes of the calcified cell accepting or effecting an union with the 

 peripheral ends of the elongated granular nuclei or nucleolar cavitiest 



(1) The term 'granulation des areoles,' used by the French Academicians in referring 

 to my observations in support of the theory of centripetal calcification of the pulp, expresses 

 the appearance produced by the nuclei, which are converted into the dentinal tubes, as seen 

 in the area of their parent dentinal cell. 



