462 HUMAN DENTITION. 





there, anastomosing, or terminating in the calcigerous or dentinal 

 cells.(l) 



The lateral ramuli are more numerous in the fang than in 

 the crown ; here the finer branches are most abundant at the 

 peripheral extremities of the tubes, which frequently appear to 

 end abruptly, as if truncated ; sometimes dividing and sub-dividing 

 quickly ; the terminal divisions diverge widely, and appear to end 

 in the stratum of fine cells which divides the dentine and enamel : 

 here and there I have seen a tube bending back to form an anas- 

 tomotic hoop with an adjoining tube. The peripheral stratum of 

 minute cells receiving the terminal ramifications of the calcigerous 

 tubes and forming the boundary between the dentine and enamel, 

 is the most sensitive part of the dentine : it is not, however, so 

 distinct a tissue as to merit a special name. (2) 



In the bicuspids (3) a larger proportion of the tubes proceeding 

 from the summit of the pulp-cavity are vertical than in the canines 

 or incisors, and a still greater proportion in the broad-crowned mo- 

 lars, (4) The tubes going to the apex of each cusp or tubercle are the 

 most vertical, and the surrounding tubes begin to incline from 

 the perpendicular in proportion as they terminate nearer the base 

 of each cusp : in the interspaces of the cusps, therefore, the tubes 

 incline towards each other. At the early stage of the calcification 



(1) PI. 123, fig. 1, d'. These cells, defined in my Report to the British Association in 

 1838, (vol. VII, p. 144) as " calcigerous cells, which form numerous layers generally ar- 

 ranged parallel with the contour of the cavity of the pulp, and most numerous at the circum- 

 ference of the ivory," are untruly indicated by the exaggerated expression that ' the inter- 

 tubular substance is cellular' ; they would be sought for in vain as cells, in the interspaces 

 of the tubes. The true dentinal or calcigerous cells include many tubes and intertubular spaces, 

 and it is much more exact to say that those cells include a tubular structure, than that the 

 intertubular space is cellular. The unprejudiced microscopical observer will find the tissue 

 in the intervals of these dentinal tubes, for the most part clear and structureless, as Pur- 

 kinje and Retzius have rightly described. Dr. Henle has stated that when deprived of the 

 hardening salts it tears into fibres, whose course is parallel to the tubes : this is not a satis- 

 factory indication of original structure. Sommering, von Baue des Mensch. Korp. 8vo. 1841, 

 p. 855-856. 



(2) M. Duval, who has well described the vital properties of this part of the dentine, 

 and rightly stajtes it to be the seat of the commencement of caries, has proposed to call it 

 * dictyodonte.' — " Observations Anatomiques sur I'lvoire," 8vo. 1839, p. 14. 



(3) PL 122, fig. 4. (4) lb. fig. 6 and 7. 



