OF THE rOISON-FANGS IN SERPENTS. 415 
The other kind of tooth witli which the poisonous serpent 
is armed, is the fang, placed in the upper jaw on either 
side, and firmly fixed into a small moveable bone, generally 
considered as the superior maxillary. Two muscles moving 
this bone, and so contributing to give motion to the fangs, 
pass through the poison-gland, situated immediately below 
and behind the eye, so that by one and the same action the 
fangs are driven into the animal or object attacked, and the 
poison is forced from the central cavity or collection of 
cells in the gland into the duct by which it is conveyed to 
the base of the fang, and thence into the canal of the tooth. 
The structure of the bones, into which the fixed or active 
fangs are inserted, is very peculiar ; nor do I remember to 
have found its analogy any where, excepting in some fishes. 
The lower surface of the bone, or that which regards the 
mouth, and into which the fang is fixed, presents a con- 
siderable cavity, divided, as it were, into two portions, into 
one of which a poisonous fang is fixed,- — the other cavity 
being reserved for the supplementary tooth intended to fill 
it at some future period. The edges of the bone are un- 
equal; and its base exceedingly vascular, dark -colon red, 
and, as it were, cellular, and is apparently undergoing a 
perpetual decay and renovation on its margin. A very 
remarkable, and so far as I have observed, a constant ap- 
pearance is, that, on one side of the jaw, the cavity for re-. 
eeiving the supplementary tooth is external, whilst on the 
other side it is internal ; or, which comes to the same thing, 
the poisonous fang is fixed on one side into the external 
portion of the upper maxillary bone, whilst on the opposite 
side it is fixed into the internal portion of the correspond- 
ing bone. 
I have already remarked, that there is always ample 
room for two fangs, though most generally there is but one 
fixed on either side. In a future part of the pc'r}»er, I have 
