Medical Officers of the Army of India.

81

minimal lethal dose for animals of the same species and weight. The treat-
ment was followed by no appreciable effect, but 2 days later a dose of 0.0005
gramme was followed by marked drowsiness. After this a series of gradually
increasing doses of venom was steadily introduced at intervals of a few days'
duration for a period of 11 months, at the close of which the animal was
taking 0.05 gramme, or 20 times a minimal lethal dose, without showing any
appreciable symtoms of intoxication. An interval of 5 weeks was now
allowed to elapse, and a dose of 0.05 gramme again administered without giving
rise to any symptoms. After another interval of 2 months' duration 0.05
gramme was once more administered, and was followed merely by a certain
temporary amount of dulness. Unfortunately, the continuation of the experi-
ment was prevented owing to the death of the animal some time after the
last occasion on which venom had been administered and before the interval
of 4 months, which was to have elapsed ere renewed treatment was under-
taken had been completed.

   This experiment is of course an imperfect one, as it does not absolutely
determine the length of time to which artificial immunity, arrived at by
habitual treatment with venom, lasts; the data do not determine whether it is
temporary or permanent, but they are at all events sufficient to show that it
differs from that which is capable of arising under the influence of treatment
with antivenene in being of a very persistent character. The phenomena do
not, as in the case of the immunity arising in connection with the use of
antivenene, indicate the mere introduction of a ready-made antidote which is
capable of retaining its activity for a certain time after entering the circulation,
but the establishment of a local manufacture of an antidote within the system.
They are only explicable as dependent on the fact that the access of the venom
to the system not only gives rise to intoxication, but to the reactive, systemic
manufacture of an antidote which constitutes the active principle which is
present in the preparations of serum which are described as antivenenes.

   (2 ) Experiments on the effects produced by ingestion of Cobra-venom.

   Experiment II. —A monkey (Macacus rhesus ) was treated with doses of
cobra-venom for a period of 16 months. During this time it invariably
received at least one dose per week, and each of these habitual, methodical
doses latterly contained 0.1 gramme of dried venom. During the greater part
of the time, moreover, it received a large number of additional casual doses
weekly, as, after it had been ascertained that the ingestion of the venom gave
rise to no appreciable symptoms of intoxication, any residual solutions of
venom, such as were constantly in hand in connection with the conduct of
other experiments, were at once administered to it in place of being thrown
away or stored up. A minimal lethal dose of dried cobra-venom was finally
administered to it.

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