THE DENTAL TISSUES. 65 



the Teeth," 1839), says, "in breaking fine sections of the 

 teeth perpendicularly to the fibres, he has frequently seen the 

 latter projecting a little at the fractured edge. In such 

 cases they are quite straight and not curved, and seem 

 to be not at all flexible. Hence it follows that the tubes 

 have an organised basis, a membrane, and that this is stiff 

 and brittle, and probably saturated with calcareous salts, 

 but weak and soft in a decalcified tooth." 



The whole importance of my father's discovery lay in the 

 fact that dentine is permeated by soft, uncertified structures ; 

 and what is yet more significant, that these soft fibrils, per- 

 meating the hard dentine, proceed from the pulp. In no 

 sense, therefore, did Henle anticipate this discovery. 



In 1854 Lent figured processes from the dentinal cells 

 (odontoblasts) which he rightly conceived to be concerned 

 in the formation of dentine ; but in the earlier editions of 

 the " Histology " of his friend and teacher, Prof. Kolliker, 

 although Lent's discoveries are described and adopted with- 

 out reservation, no mention of the real structure of dentine 

 occurs. But in the last edition, Prof. Kolliker says " after 

 Tomes had described a soft fibre in each tube, I fell into the 

 mistake of supposing that these fibres and the tubes were 

 one and the same." 



The circumstances under which the dentinal fibrils can 

 or cannot be discovered are as follows, and may be taken as 

 proofs of the distinction between the dentinal fibrils and the 

 dentinal sheaths. 



If a tooth section be submitted to the action of a caustic 

 alkali and boiled in it, or be allowed to completely putrefy, 

 so that the soft parts are entirely destroyed, the dentinal 

 sheaths can still be demonstrated, but the fibres can in no 

 way be brought into view (Kolliker). The dentinal sheaths 

 may be demonstrated also in fossil teeth, as has been shown 

 by Hoppe (Wurzburg Nat. Zeitschrift, Bd. VI. p. XL) and 

 others. 



