DEVELOPMENT OF VASCULAR DENTINE. 
31 
this explains the appearance of faint striation in the outer layer of dentine, in which 
nevertheless no tubes nor real interspaces exist. 
Some isolated odontoblast cells are shown more highly magnified in fig. 5 ; the 
constrictions in their middles are due to the shrinkage caused by absolute alcohol, 
the end next to the dentine ( q ) being apparently too rigid to shrink, and the presence 
of the oval nucleus preventing shrinkage at the opposite extremity ; examined in 
serum they are of uniform diameter. 
The odontoblasts of the Hake measure about -gy-gth of an inch in length and g oV ofh 
of an inch in diameter ; they are, after calcification has once commenced, furnished 
with a variable number of fine processes at the end next to the dentine, which 
project for a little way into it ; but they do not remain permanently uncalcified, 
like the dentinal fibres of Mammalia. The opposite end of the cell tapers off 
into a fine process, but I have never detected lateral processes connecting them 
with their neighbours. The nucleus is oval, very distinct in some of the cells, 
but sometimes indistinguishable ; I have been unable to discover under what con- 
ditions this is the case. I have described the structure of the tooth of the Hake 
at some length, because I am not acquainted with any description of it in the pages 
of writers on odontology, nor with any other tooth which so clearly exemplifies the 
true nature of this kind of vaso- dentine. But before proceeding to remark upon 
the teeth of certain other Gadidse, I will quote Betzius’ description of the dentine 
of the Ling. 
As quoted by Nasmyth (‘ On the Teeth, 1839,’ p. 107,) Betzius thus described the 
dental tissues of the Ling “ Along the wall of the cavity of the pulp, which ran 
longitudinally, and was in part tubiform, the main tubes opened with short trunks of 
from yg- to ygr'" p.m. (yyoth of an inch, about) in thickness, which ran towards the 
apex and in an outward direction, and gave off branches on both sides, between 
which there were considerable intervals ; these branches formed, with others of the 
contiguous tubes, large loop-shaped anastomoses, and their outer extremities entered 
also into closed anastomoses, almost like the more minute blood-vessels in the villi of the 
abdominal canal” 
“ The more minute lateral branches of the tubes of the dental bone in the Ling 
were not easily discovered ; they appeared to be less regular, and generally ran in a 
direction transverse to the tubes from which they rose, or parallel to the axis of 
the tooth.” 
From the passage which I have italicised, it will be obvious that Betzius suspected 
the true nature of the contents of the larger canals which permeate the tooth of 
the Ling, and Professor Owen’s name of vaso-dentine would imply the same interpre- 
tation, but the latter’s more detailed description does not confirm the supposition 
that he believed the tubes to be occupied by capillaries and capillaries alone. 
Thus he writes of the dentine of the Gadidse “ Processes of the pulp are 
conveyed by medullary canals which diverge from all parts of the main central 
