QUARTERLY CHRONICLE. 95 



attention are, first, the mode of termination of the nerves of 

 the tooth, Avhich is a subject as yet but little investigated ; and, 

 secondly, the relation of the intcrtubular dentine substance of 

 the tooth to the tooth-pulp, and the development of the former 

 from the latter. He has found the long incisors of Rodents 

 admirably adapted to this investigation, and in examining 

 the nerves has made use of the terchloride of gold, which 

 was lately recommended by Cohnheim, and used by him in 

 the investigation of the nerves of the cornea. With regard to 

 the first of these matters in question, he states that extremely 

 fine nerve filaments pass between the pulp-cells, and penetrate 

 the dentine of the tooth, just as do the processes from the 

 peripheral cells of the pulp : hence it is necessary to distinguish 

 two sorts of dentinal canals — those which contain processes 

 from the pulp-cells, and those which contain nerve-fibres. 

 (See Plate II, fig. 3) . Three views as to the origin of the inter- 

 tubular substance of the dentine have been current : one is 

 KoUiker's, who conceives it to proceed from the calcification 

 of a soft matrix excreted from the dentinal cells and their 

 thin prolongations; the second is Waldeyer's, who modifies 

 KoUiker's view considerably, and denies the existence of a prse- 

 formative membrane to the pulp. He maintains that the forma- 

 tion of the dentine consists in the conversion of a part of the 

 protoplasm of the dentinal cells into a coUaginous substance, 

 which is subsequently calcified, while the remaining part of 

 the cell-protoplasm continues in the form of soft fibres to 

 occupy the interior of the tube surrounded by the calcified sub- 

 stance (figs. 1, 2) . H. Hertz, in a paper published in Virchow's 

 ' Archiv,' 1866, states that the intcrtubular substance of the 

 dentine is the chemically changed and calcified intercellular 

 substance of the pulp-cells. Herr Boll proceeds to discuss 

 the views of Waldeyer and Hertz, but fact after fact has 

 convinced him that Waldeyer is correct. He gives several 

 figures of the peripheral-cells of the tooth-pulp — the odonto- 

 blasts — with fromone to four processes projecting into the 

 dentine substance. One of his sections (fig. 2) shows the cells 

 completely detached from contact with the dentine, excepting 

 through their long, fine processes ; and it is most clearly seen 

 that there is no connection between the hard substance of the 

 dentine and any intercellular matter of the pulp : in fact, 

 no such intercellular matter exists at the periphery. The 

 limitation of the hard substance of the dentine where it comes 

 in contact with the cells of the pulp is termed memhrana eboris. 

 The multiplicity of processes from the odontoblasts, instead of 

 a single fibril, as originally described by Lent, is an interest- 

 ins: observation. 



