PHYSIOLOGICAL ACTION OF VENOM OF BLACK SNAKE. 219 
height, a further injection, containing ten or twenty times the 
former quantity be made, this causes.a second drop in the blood 
pressure. The fall is, however, in no way so great as in the 
first instance, notwithstanding the fact that the quantity injected 
is so much larger, and whereas the recovery from the cardiac 
depression due to the first dose, was not complete until from forty 
minutes to one hour, the pressure regains the normal, or about 
the normal, in fifteen minutes after the second injection. If, after 
this second recovery, a third dose of the poison, of the same quantity 
as the second injection (or even double that quantity) be introduced, 
it has little or no effect upon the blood pressure. The only explan- 
ations of such results are either that the cardiac muscle has 
become much less sensitive to the operation of the poison, or that 
in the meantime, some body possessed of properties which interfere 
with the operation of the poison, has become present in the blood 
plasma. This point, however, opens up the whole problem of 
immunity and the protective reaction of the organism against the 
poison, which I hope to discuss at some future time. 
Precisely the same result was observed by Wooldridge when 
nucleo-albumens were repeatedly injected, and the enormous fall 
in blood pressure produced by injecting albumoses into a vein, 
does not occur if a second injection be made after the animal has 
recovered from the first. . 
Protocols of Experiments showing the influence of the Venom upon 
the Arterial Blood Pressure. 
These experiments were performed on dogs and rabbits. The 
Poison was introduced either intravenously, subcutaneously, or 
Into the peritoneal cavity. Most of the experiments in which the 
Poison was injected into a vein were made upon dogs, whereas in 
those cases where subcutaneous injection was employed, rabbits 
Were used. Graphic records of the blood pressure were taken 
"pon a Hering’s kymograph by means of a mercury manometer. — 
The time and duration of the injection was indicated by raising 
the signal line. Underneath the signal line a time marker con- 
nected with a seconds clock gave the value of the abscissa. In 
