8
Hoplocephalus curtus has any hindering effect on this action of the poison. A
single experiment was now sufficient to show that C. V. serum had likewise no
effect of an antitoxic nature against this clotting action of daboia venom in vivo,
(vide protocols, Table VIII).
In one of the communications mentioned above, I pointed out that, if a quan-
tity of daboia venom not sufficient to cause rapid death by intravascular throm-
bosis be injected, a negative phase of diminished blood coagulability sets in, and
that, while the blood is in this condition, the injection of a large quantity of the
same poison cannot so increase the coagulability as to cause thrombosis. In a
paper16recently read before the Royal Society, Rogers has pointed out that, if a
preliminary non-lethal dose of venom be given, followed by a larger amount after
the phase of diminished coagulability of the blood has set in, quite rapid death
could be brought about, in spite of the fact that there was no intravascular throm-
bosis produced. Further, this observer made a prolonged investigation of this
phenomenon and arrived at the conclusion that the primary cause of death in
these cases was a complete paralysis of the vaso-motor centre in the medulla. In
the case of large animals, such as man, bitten by a daboia he considers that
death in most cases will result from this action of the poison. It became, there-
fore, of great interest to test C. V. serum and H. C. V. serum against this action
of daboia venom. The method adopted was as follows : a small non-lethal
dose of venom was given intravenously. Half an hour afterwards a mixture
containing 4 c.c. of one or other serum and a quantity of poison just capable of
causing fairly rapid death by vaso-motor paralysis was injected also intravenously.
The constituents of this mixture had been standing in contact for half an hour
previous to the injection. A reference to the protocols (Table IX) will show
that the two animals which received the sera died in practically the same time as
the control. It is evident, therefore, that neither of the sera had any neutralising
effect for this action of daboia venom.
ECHIS CARINATA (PHOORSA).—The physiological action of this venom, as
far as I have ascertained from a number of preliminary observations, is similar
to the action of daboia venom. It is, however, of considerably greater toxicity.
Thus, a dose of 0.05 milligramme per kilo. injected intravenously into a rabbit can
cause rapid death, the result of intravascular clotting. A smaller amount than 0.05
milligramme per kilo. is non-lethal, but causes a negative phase of diminished
coagulability. Further, the action of this poison resembles the action of daboia
venom inasmuch as, if after a small non-lethal dose a larger quantity be injected,
rapid death ensues, and in these cases no intravascular clotting can be demon-
strated. Although I have not investigated this phenomenon, it is probable that
we are dealing in this case also with a paralysis of the vaso-motor centre in the
medulla. It was, therefore, necessary to test the two sera under consideration
against both these actions of the venom.
In the first place, they were tested with two minimum clotting doses, namely,