PHYSIOLOGICAL ACTION OF VENOM OF BLACK SNAKE. 181 
As the fluid plasma of the negative phase after venom injections 
presents, in many respects, the closest analogies with the plasmas 
obtained by both of these means, I made a series of experiments 
to determine the influence of calcium on the coagulability of the 
blood of animals after injections of venom. The effect of calcium 
salts on plasmas in vitro, has already been mentioned. 
I found that the results of these experiments could be arranged 
in three classes— 
(1) The cases where only a very moderate negative phase has 
been produced, and the clotting of the shed blood is delayed 
from thirty minutes to two or three hours. 
(2) Cases in which the negative phase is more pronounced and 
the shed blood clots only after some hours or days. 
(3) Very pronounced negative phases in which the blood never 
clots spontaneously, and in which the addition of saturated 
solution of sodium chloride etc. only occasions a very small 
amount of coagulum. 
The addition of a few drops of calcium chloride to a sample of 
blood from the first class, causes almost immediate solidification 
and if a few cc. of a 1% solution of this salt in ‘9% NaCl be 
Injected into a vein, the coagulability of the blood is raised above 
the normal, and very frequently the animal dies in a few minutes 
from extensive thrombosis. 
2 
a 
a 
ah 
With the second class, the calcium chloride is without influence 
i the extravascular plasma, but raises the coagulability of the 
ireulating blood towards the normal. 
. ‘With the third class, CaCl, has no effect either when injected 
or added to the plasma in vitro. 
; = following three experiments, chosen from a large number, 
illustrate these effects of calcium salts. In these experiments the 
ala artery and jugular vein were dissected out, and cannule 
lied in both. The former was used for taking samples of blood, 
nd the latter for the introduction of the venom and calcium 
