8 T. C. WHITE ON THE SO-CALLED '^ NERVE" OF THE TOOTH. 



returning vein ; tracing this thread into the pnlp we shall readily 

 distinguish the nerve as a bundle of parallel fibres which, running 

 in together a short distance, divide into two, three, or four fasciculi, 

 and dividing again still give off fibres to every part of the pulp ; 

 it is highly probable that these fibres end in loops, but the pressure 

 necessary to reduce the pulp sufficiently thin for observation rup- 

 tures the loops, and consequently they very frequently appear to 

 terminate in free extremities ; but one fact may be easily demon- 

 strated, namely, their course is always at right angles with the 

 dentinal tubuli. Besides the ramifications of the dental nerve the 

 pulp also contains the branches of the artery and its vein; these 

 are not so easily followed, but in an examination of the pulp of a 

 tooth extracted for severe inflammation in it, the congested vessels 

 were naturally injected, and could be seen as a complicated net- 

 work without any definite arrangement excepting a loop -like dis- 

 tribution towards the circumference ; in some cases the vessels of 

 the pulp, becoming stained by the carmine, will be readily seen 

 with their peculiar transverse nuclei and distinguishable from the 

 areolar tissue, whose nuclei are spindle-shaped. There is one feature 

 in the microscopical examination of this prepared pulp which will 

 not escape observation — it is the curious arrangement of its cortical 

 portion. In referring to the microscopical appearance of the ex- 

 terior of the pulp, as it appears on first splitting a tooth, I alluded 

 to the comparative likeness presented by it to that of the dentine 

 cut across the tubes, and if that comparison is borne in mind in the 

 examination of this external portion of the pulp, under its present 

 circumstances, we may easily interpret the meaning of this arrange- 

 ment. The cortical substance of the pulp in its healthy condition con- 

 sists of a number of oval bodies placed side by side with their long 

 axes perpendicular to the surface of the puljD on which they stand ; 

 they are deeply stained by the carmine, which proves that they are 

 endowed with active and growing powers. These oval bodies are 

 termed '' Odontohlasts.''^ An examination of an odontoblast, which 

 has been isolated by pressure from the others, will show that it has 

 an attachment by a transparent structureless appendage to some- 

 thing within the body of the pulp, while a similar appendage, pro- 

 ceeding from its distal extremity, penetrates a tubule in the dentine, 

 and becomes the dentinal fibril of Tomes. 



The odontoblastic layer of the pulp is so important an element 

 in the life and histology of a tooth that its history deserves a closer 



