THE DENTAL TISSUES. 71 



precisely the same tissue. He would prefer to speak of 

 dentine as being a fibrillar tissue included in a hard and 

 homogeneous matrix. 



These views, however, do not differ substantially from, 

 those in the text, save that M. Magitot does not recognise the 

 existence of that transitional tissue which others believe to 

 be there, and call the sheaths of Neumann. 



No true nerve fibril has ever been seen to enter the den- 

 tine ; nothing but the dentinal fibril has ever been proved 

 to pass from the pulp into the hard substance of the 

 tooth ; nevertheless, the observation of Boll is very sug- 

 gestive. He found that by treating a perfectly fresh pulp 

 with per cent, solution of chromic acid an immense 

 number of fine fibres could be demonstrated, a great many 

 of which projected from above the surface, as though they 

 had been pulled out of the dentinal tubes ; but although 

 they pass up from a plexus of dark-bordered nerve fibres 

 beneath the membrana eboris, between the cells of that 

 layer, their passage into the dentine remains a mere matter 

 of inference. 



Boll's observations likewise are awaiting confirmation or 

 disproof, and so far stand alone. 



Be that as it may, there can be no question that the 

 sensitiveness of the dentine is due to the presence of soft 

 organized tissue in the tubes, and is not a mere transmission 

 of vibrations to the pulp through a fluid or other inert 

 conductor. The peripheral sensitiveness of a tooth can be 

 allayed by local applications which it would be absurd to 

 suppose were themselves conducted to the pulp ; moreover, 

 it is within the experience of every operator that after the 

 removal of a very sensitive layer of caries, you often come 

 down upon dentine, which, though nearer to the pulp, is 

 far less sensitive, a condition quite inexplicable, except 

 upon the supposition of a different local condition of the 

 contents of the tubes. Irritation applied to the dentinal 



