DENTINE 243 



several times in dentine is shown in fig. 123, previously 

 referred to, where a transverse dentinal tube anastomosing 

 with several normally-directed longitudinal ones is seen. 

 ft is very difficult to account for this condition, but in 

 one unerupted human premolar a similar arrangement of 

 the tubes was seen in many places around the circumference 

 of the pulp. 



The Dentinal Tubes. As seen in a drv section, the tubules Fine 



"U "U * 



of the dentine arise by open ends at the periphery of the O f ^ e " 

 pulp cavity and gradually become narrower as they extend tubes. 



FIG. 147. Branching of dentinal tubes (silver pyridin). ( x 150.) 



throughout its substance, terminating at the cement and 

 enamel margins in very fine subdivisions or branches. These 

 fine branches are, however, not confined to the terminations 

 of the tubes, but suitable stains show their presence in all 

 parts of the dentine (see figs. 147-151). Referring to these 

 fine ramifications of the dentinal tubules, Rose says (19) that 

 at the edge of the dentine the ramifications represent a true 

 dichotomous branching of the dentinal tubes, and that 

 this occurs but rarely in the portions of the dentine nearer 

 to the pulp ; in the preparations from which the accompany- 

 ing illustrations are taken such a termination of the tubes 



R 2 



