NERVES TO ODONTOBLASTS, AND ON THE GROWTH OF DENTINE. 323 



varying distances. These had been drawn out from the dentinal tubules and now lay 

 free (Fig. 4). In one case the dentinal fibre could be seen springing from its odonto- 

 blast and apparently giving off its lateral branches, the latter, however, being mere 

 rudiments. In other situations, odontoblasts were seen which had become separated from 

 the other cells and had drawn out along with them their internal or root process. This 

 was in some cases of great length and could be traced for some distance into the pulp. 

 In other cases part of the dentinal fibre still remained attached to one extremity of the 

 separated odontoblast, while from the other extremity the long internal root process was 

 seen extending into the pulp. 



I have not in the course of my reading observed any allusion to the great length of 

 this internal process of the odontoblast ; on the contrary, Waldeyer's description is gener- 

 ally adopted, according to which it is very short and constantly connected with one of 

 the cells lying immediately beneath the membrana eboris. According to Hertz the pro- 

 cess does not exist. I would therefore again direct attention to its great length, to the 

 absence of lateral branches, and to the oval, fusiform, or pear shape of the odontoblasts in 

 the tooth of the ox. 



On snipping off small pieces of the outer surface of the pulp, and teasing them in a 

 l / o solution of osmic acid, the specimens showed clearly the nerve fibres isolated and run- 

 ning amongst the odontoblasts, but the latter adhered closely to one another and could 

 not be separated by teasing, and thus it was impossible to trace the nerve fibres to their 

 ultimate destination. In order to render the cells more easily separable, some pulps 

 were placed in a 0*6°/ o solution of potassium anhydrochromate for 24 hours. Fragments 

 from their outer surface were then teased in picrocarmine, with the result that the long 

 central process of the odontoblast was rendered very evident (Fig. 5). These central 

 processes ran into the pulp towards the nerves, and could often be traced inwards to a 

 distance greater than six to twelve or more times the length of the odontoblast itself. 

 From the opposite extremity of each odontoblast the dentinal fibre proceeded, and in 

 many cases this was also exceptionally long. The central process arises from each 

 odontoblast gradually, the proximal end of the cell gradually tapering till it becomes the 

 pulp process. The distal extremity of the odontoblast, on the contrary, rapidly narrows 

 down to a fine fibre, which is continued onwards as the fibre of Tomes. The nucleus of 

 each cell seems to be swollen up, and is in these preparations a large oval body filling up 

 a large part of each odontoblast. When examined by a high magnifying power each 

 odontoblast appears almost as if a mere fusiform enlargement of the continuous fibre 

 formed by the long root process and the dentinal fibre with a large nucleus in the 

 dilated part. 



The next point was to trace the further connection of the root process of each odonto- 

 blast. Many preparations of pulps treated with the potassium bichromate solution were 

 made and carefully examined in order to find if there were any connection between the 

 root process and the nerve fibre. I am convinced that the central processes of the 

 odontoblasts become continuous with the nerve fibrils. The connection is extremely 



