64 VIPERADA. 
Philosophical Transactions for 1818. This tube, although | 
completely enclosed, excepting at its basal and apical 
orifices, must be considered as formed merely by the 
closing round of a groove in the external part of the tooth 
itself, and hence not in any way connected with the inner 
cavity of the tooth, in which exists the pulp upon which 
the substance of the tooth is formed. The base of the 
tooth, and consequently the basal orifice of the tube just 
described, is embedded in a sac, into which the poison is 
poured from the ducts of the glandular structure by which 
it is secreted, and which is believed to represent the 
parotid gland of the higher vertebrata. The poisonous 
fluid itself is inodorous, tasteless, and of a yellow colour. 
It is secreted in greater quantity, and its qualities are 
more virulent in a high temperature than in cold. Its 
secretion may be greatly increased by local irritation; as 
is evidenced by the following fact. Some years since I 
was dissecting very carefully and minutely the poison 
apparatus of a large Rattlesnake, which had been dead 
for some hours; the head had been taken off immediately 
after death; yet as I continued my dissection the yellow 
poison continued to be secreted so fast as to require to be 
occasionally dried off with a bit of rag or sponge; I be- 
lieve that there could not have been less altogether than six 
or eight drops at the least. 
When the animal inflicts the wound, the pressure on the 
tooth forces a small drop of the poison through the tube ; 
it passes through the external orifice, which is situated on 
the concave side of the curved tooth, and is in the form of 
a slit. The manner in which the blow is inflicted is ag 
follows. The animal generally throws itself in the first 
place into a coil more or less close, and the anterior part 
of the body is raised. The neck is bent somewhat abruptly 
