Xliv INTRODUCTION. 



are proceeding, the calcareous salts of the surrounding plasma begin 

 to be accumulated in the interior of the cells, and to be aggregated 

 in a semi-transparent state around the central granular part of 

 the elongated nuclei, which now present the character of secon- 

 dary cells, and the salts occupy, in a still clearer and more 

 compact state, the interspaces of such cells (ib e') : the elongated 

 granular matter of the terminally confluent secondary cells 

 establishes the area of the tubes, by resisting, as it would seem, 

 the encroachment of the calcareous salts ; the nuclear tracts (ib. /.) 

 receiving a smaller proportion of the salts, in the condition of 

 minute disgregated particles, which are usually arranged in a 

 linear series of nodules, and contribute to cause the white colour 

 of the moniliform area, of the tube when viewed by reflected 

 light, and its opacity when viewed by transmitted light. Thus 

 the primitive existence of the granular nuclei, their multiplication in 

 the primary or parent cell, their elongated form, their serial arrange- 

 ment end to end, and terminal confluence, are indicated in the calcified 

 pulp by the arese of the dentinal tubes (fig. 2, c) ; the interspaces of 

 the metamorphosed nuclei being occupied by calcareous salts in a 

 clearer and more compact state, with evidence, however, of a dis- 

 tinctness of the nucleolar membrane or secondary cell (fig. 2, b) from 

 the cavity of the common containing cell, which sustains the interpreta- 

 tion of the proper parietes of the dentinal tube. The indications of the 

 primitive boundary or proper parietes of the parent-cell (fig. 2, a) are 

 in like manner more or less distinctly retained, through a modification 

 of the arrangement of the calcareous salts in the boundaries and in 

 the interspaces of the cells. The salts are sometimes blended with 

 the blastema in these interspaces in a disgregated condition which 

 renders them almost as opake as the arese of the tubes. When 

 a layer of the calcified cells is carefully detached, the exposed 



