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to investigate further this action in vitro of these two venoms, the only two
which were available to me at the time.

   After many failures to get any definite results by the method followed by
the older investigators, namely, the method of allowing fresh blood to flow
directly into a solution of venom, I was led to use blood which was kept liquid
by the addition of citrate of soda. At a later date I found that similar results were
obtained with citrate and oxalate plasma, which had been completely freed from
the red corpuscles by allowing these latter to sediment, and then syphoning off
the clear supernatant fluid.

   The observations, therefore, which I have now to record naturally fall into
two groups, as follows :—

     (1) Observations on the action of cobra and daboia venoms on the
coagulability of citrate whole blood.

     (2) Observations on the action of cobra and daboia venoms on the
coagulability of oxalate and citrate plasma freed from red cells.

The action of cobra and daboia venoms on the coagulability
of citrate whole blood.

   The blood which was used in these experiments was got from rabbits in the
following manner. By means of a cannula in the femoral artery, a measured quan-
tity of blood was run into a measured amount of a 20 per cent. solution of sodium
citrate. These quantities were so arranged that the citrate of soda was in the
proportion to the blood of 1 to 100 or 1 to 50. In the protocols of the experiments
it is invariably recorded in which of these proportions the citrate was present.

   The citrate blood was then divided up into a series of small test tubes, 1 c.c.
being accurately measured into each test tube. By direct experiment was
then ascertained the minimum amount of a solution of calcium chloride of
known strength which it was necessary to add to each cubic centimetre of cit-
rate blood so as to cause solid clotting in from 1 to 3 minutes, and likewise the
maximum amount of calcium chloride solution which could be added without
causing any clot in from 4 to 6 hours or longer.

   It was found that these quantities of lime solution varied slightly with each
sample of citrate blood used, however carefully the solutions of citrate and of
calcium chloride were prepared, and however accurately the blood was measured
and divided up. It was, therefore, necessary to make careful control experi-
ments, such as I have indicated, for each series of observations, that is to say,
for every different sample of rabbit's blood which was used.

   Let us first consider, then, the action of cobra venom on plasma as shown by
its effect on the coagulability of citrate whole blood. In view of the fact that
cobra venom does not, even when introduced in large quantity directly into the