OF THE POISON-FANGS IN SERPENTS. 
nutrition alters, as it now receives its nourishing vessels 
from the centre of the bone itself, through which may be 
traced a canal filled with soft parts, and communicating by 
a large orifice with each of the fixed teeth. The periods 
at which the animal casts or sheds these teeth are unknown 
to me, but one would naturally conjecture that it may be 
annual : the subject is open to the inquiries of the natural- 
ist. 
It has been already observed, that the simple teeth, even 
in poisonous serpents, are not confined to the lower maxil- 
lary bone and to the palate-bones in the upper jaw, but 
are found in certain serpents, implanted also into the supe- 
rior maxillary bone. Mr Schreider first noticed them in 
the Hydrus or Water-Snake; and they have also been 
found in the Boa Jasciata^ Boa iineaia, &c. ; likewise in 
the serpents called Trimeresures by the Count Lacepede. 
These have with propriety been separated from the other 
venomous serpents, or those which have only poison-fangs 
in the upper maxillary bone, and which have been arranged 
by naturalists under the classes Crotalus and Vipera. The 
essential character of this class is, their having only poison- 
ous fangs in the superior maxillary bone, and, consequent- 
ly, in having the simple teeth confined to the palate-bones 
in the upper jaw, and in the lower to the inferior maxillary 
bone. I have found this character unequivocal and con- 
stant in all the poisonous serpents I examined in Africa ; 
in the Rattle-Snake, in the common Viper of this country : 
but I was surprised to find that several varieties of snakes, 
described by Mr Russei as varieties of the celebrated Mqja, 
or Spectacle-Snake of India, have simple teeth implanted 
in the superior maxillary bone. I first observed this fact 
in a specimen of a snake given me as a Cobra, and which 
belonged to an Indian collection sent to the Museum. On 
observing that there existed a simple tooth in each of tlie 
