INTRODUCTION. Ixi 



crown of a complex molar are lodged in cavities on the exterior 

 of the enamel. These exterior cavities of the cement are formed 

 by centrifugal extension of the calcifying process in the blastema 

 in which the cells are imbedded. The calcareous salts penetrate 

 in a clearer and more compact state the cavity of the cell, but 

 their progress is arrested apparently by the nucleus which maintains 

 an irregular area, partly occupied by the salts in a subgranular 

 opake condition, but chiefly concerned in the reception and transit 

 of the plasmatic fluid which enters and escapes by the minute 

 tubes which are subsequently developed from the nucleolar cavity 

 as calcification proceeds. The radiated cells or cavities (/) thus formed, 

 are the most common characteristic of the cement, but not the 

 constant one. The layer of the capsule which surrounds the crown 

 of the Human teeth and of the simple teeth of Quadrumana and 

 Carnivora, consists simply of the granular blastema, without nu- 

 cleated cells, and the radiated corpuscles are, consequently, not 

 developed in the cement which results from its calcification. In 

 the thicker parts of the inflected folds of the capsule of the 

 complex teeth of the Herbivora traces of the vascularity of that 

 part of the matrix are persistent, the blastema calcifying around 

 certain of the capillaries and forming the medullary canals. The 

 varieties of these canals are traversed by minute tubules continued 

 from or communicating with the radiated cells. These tubules, and 

 the more parallel ones which traverse the thickness of the cement in 

 many Mammalia, are the remains of linear series of the minute 

 granules of the blastema. 



In the deep sockets of the teeth of persistent growth the 

 matrix is maintained by the constant additions of new blastema 

 and cell-material to the bases of the dentinal, enamel and cemental 

 pulps. I have demonstrated the partial growth of the enamel pulp 



