180 



ON THE ELEMENTARY PARTS OF THE HUMAN FABRIC. 



Fig. 82. Fig. S3. 



f 



Vessels of Dental Papilla. 



files of nuclear matter are formed, which 

 present an unbroken continuity from 

 one primary cell to another. While 

 these changes are proceeding, the cal- 

 careous salts furnished by the blood 

 begin to be accumulated in the interior 

 of the cells, and to be aggregated in a 

 semi-transparent state around the cen- 

 tral granular part of the elongated nu- 

 clei, which now present the character 

 of rows of minute secondary cells ; and 

 the salts occupy, in a still clearer and 

 more compact state, the cavity of the 

 primary cell not occupied by the trans- 

 formed nuclei. The rows of minute 

 secondary cells (which appear scarcely 

 to advance beyond the condition of 

 simple granules) remain uncalcified in 

 the midst of the solid calcareous sub- 

 stance ; and thus constitute the tubuli 

 of the dentine, in which a granular or 

 bead-like aspect may generally be traced. 



214. Around the tubes, in a transverse section, is a small circular space 

 (Fig. 84, 6,) manifestly distinct from the intertubular substance; and this is 

 regarded by Professor Owen as the indication of a membrane surrounding 

 the elongated and coalesced secondary cells. The traces of the original 

 boundary of the primary or parent-cells (Fig. 84, , a), are generally lost; 

 but, as already remarked (210) they are sometimes preserved with suffi- 

 cient distinctness to be quite recognizable. The " primary curvatures" ob- 

 servable in the tubuli are due to the arrangement of the original linear series 



Diagram of development of Dentine ; a, end 

 of a linear series of primary deminal cells ; 6, 

 cells with nuclei dividing ; e, subdivision and 

 elongation of nuclear mailer; d, elongated 

 nuclei uniting to form the area; of dentinal 

 lubes; e, e, calcified cap of dentine, formed by 

 the mtus-susception of the clear hardening 

 salts into the walls and cavities of the cells 

 and intercellular blastema f, e, and by their 

 partial exclusion from the monilifonn nuclear 

 tracts/ 1 f ; g, union of two peripheral nucle- 

 olar or secondary cells with one nearer the 

 centre of the pulp. 



