A 
tooth of our common Black Snake, ( Coluber constrictor, Linn.,) 
from an alcoholic specimen, procured for me by my friend, Mr. 
F. W. Putnam, of Salem. This preparation is drawn in the plate. 
This egg-tooth represents in its structure all the character- 
istics of the teeth of snakes and lizards generally ; and being at 
the same time small enough to allow a high power of the 
microscope, it is the best object I know, for studying that kind 
of teeth. 7 
The central cavity is bottle-shaped, and is entirely filled with 
the yellowish pulp, in which were seen the contours of large 
balls. Upon and around this central pulp rests the hard tooth, 
flattened out about the margin, consisting of Dentine (Substan- 
tia eburnea) penetrated by its canals (Canaliculi dentin.) 
These canals, raying out from the cavity of the pulp towards 
the margin like a fan, open into that cavity, and contain, when 
fresh, a yellowish fluid, but soon they become white by drying 
and successive reception of air. They run out first in large, 
simple canals, often a little undulated; but soon they branch, 
and the branches anastomosing with each other, form a net- 
work of very fine capillaries. As this network does not reach 
the periphery of the tooth, there remains a broad margin 
entirely solid and transparent, like glass. This is the sharp 
cutting edge. Irom the analogy with other teeth, and from a 
view with a lower power of the microscope, one would suppose 
that this transparent margin was an enamel crown extending 
all over the tooth, but even with a very high power, I could 
not find any trace of the characteristic polygonal fibres, and we 
can state that this margin of the tooth is also composed of one 
and the same homogeneous dentine, as the rest. 
There was no trace visible of either a blood-vessel or nerve 
reaching into this pulp. With man and mammalia, this is 
characteristic of a very old tooth; but with this egg-tooth, 
which is on the contrary very young, the drying of the nutri- 
tive organs indicates nothing but their short duration. After 
the drying and dying of those organs, and the consequent dry- — 
ing of the pulp and the fluid in the canals of the Dentine, the 
tooth is only held mechanically in its socket, and being not 
very deeply set, 1s rubbed off by the first violent contact. This 
process, of a sudden drying of life-imparting organs, is very 
like that by which the horns of the deer are cast off yearly. 
The short duration of this tooth, for it drops in one or two 
days after the hatching of the snake, accounts for its having been 
overlooked by naturalists for so long a time. Even Rathke, in 
his beautiful work on the evolution of the Ring Snake, published 
in 1839, has made no mention of it, though he describes very 
