ON THE SO-CALLED “ NERVE OE THE TOOTH. 3G3 
and gives exit to the returning vein; tracing this thread into 
the pulp 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 ne¬ 
cessary to reduce the pulp sufficiently thin for observation 
ruptures the loops, and consequently they very frequently 
appear to terminate in free extremities; but one fact may be 
easily demonstrated, 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 inflam¬ 
mation in it, the congested vessels were naturally injected, and 
could be seen as a complicated network without any definite 
arrangement excepting a loop-like distribution towards the 
circumference; in some cases the vessels of the pulp, be¬ 
coming stained by the carmine, will be readily seen with their 
peculiar transverse nuclei and distinguishable from the areo¬ 
lar 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 ar¬ 
rangement of its cortical portion. In referring to the micro¬ 
scopical appearance of the exterior of the pulp, as it appears 
on first splitting a tooth, I alluded to the comparative like¬ 
ness presented by it to that of the dentine cut across the 
tubes, and if that comparison is borne in mind in the examina¬ 
tion of this external portion of the pulp, under its present 
circumstances, we may easily interpret the meaning of this 
arrangement. The cortical substance of the pulp in its 
healthy condition consists of a number of oval bodies placed 
side by side with their long axes perpendicular to the surface 
of the pulp 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 “ Odon¬ 
toblasts” 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 
something within the body of the pulp, while a similar 
appendage, proceeding 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 examination than the limits of a paper like 
xlv, 24 
