216 C. J. MARTIN. 
(c)—Explanation of the fall in blood pressure. 
Weir Mitchell and Reichert, who observed the same diphasic : 
character in the blood pressure curve after intravenous injection 
of various kinds of snake poison, were of opinion that the primary 
fall was chiefly due to the depressant action of the venom upon 
the vaso-motor centres in the medulla oblongata, and slightly 
upon the heart, but that the ultimate fall of pressure was cardiac 
in origin. 
From the results of experiments the details of which are given 
at the end of this section of the present paper, I have come tothe 
conclusion that in both cases the fall in pressure is mainly due to 
a direct action of the poison upon the heart. The most important 
evidence which has led me to this conclusion is drawn 
(1) From observations on the blood pressure in experiments in 
which the cervical cord had been previously divided, and 
(2) From those experiments in which observation of the volume 
of the spleen or kidney were made at the same time as 4 
record of the arterial blood pressure. 
In experiments 16 and 17, the intravenous injection of 0009 
and ‘0008 gramme of venom into two dogs with severed cervical 3 
cord, produced precisely similar results to those which I ~~ 
frequently obtained with normal dogs. The only difference was: 
that in the experiments in which the cord had been previo _ 
divided the blood pressure was reduced to almost one h 
original height before the introduction of the venom. In exper 
ment 16 the larger dose killed the animal in ten minutes, and the 
pressure fell steadily until death, whereas in experiment li, 
which the dose was smaller, the animal lived for nearly t 
with moderate doses of the poison. Were the numbers ta 
in these two experiments multiplied by two, they would ¢ respon 
it te 
in 
wo hours, . 
and the blood-pressure record exhibited the same temporary a 
recovery as had been observed in the majority of the experme™” 
“6 ice 
pulated ; 
ibe r radon 
SS ED Otte ete aE eS EE ae on | ae eae DO at 
exactly with those of experiments in which the cord was intact. 
Experiments 30, 31, 32, and 33, in which a simultaneous Fe" 
: or 
of the arterial blood pressure and the volume of the kidney 
