PHYSIOLOGICAL ACTION OF VENOM OF BLACK SNAKE. 213 
the disadvantage that the injection of even very small quantities 
of the venom directly into the circulation occasions so great an 
increase in the coagulability of the blood, that this fluid frequently 
clots in the vessels. When this occurs at all extensively the 
circulation is speedily terminated and death ensues. It is indeed 
very difficult to prevent intravascular clotting, and before we can 
draw conclusions as to the action of the venom upon the heart or 
other portion of the vascular mechanism we must be sure that 
thrombosis has not occurred.!_ In wy earlier experiments I was 
not aware of this action of venom upon blood plasma, and the 
inconsistent results I obtained puzzled me greatly. The whole 
matter was however cleared up when I discovered that the 
extraordinary lack of uniformity in, and frequent sudden termin- 
ation of my experiments, was due to the arrest of the circulation 
by solidification of the blood. 
The animals used were dogs and rabbits. The results were 
substantially the same with both animals. The effect of the 
poison on the blood pressure was investigated under a variety of 
experimental conditions with and without curari. In some 
experiments the vagi were previously severed, in others not. 
Two experiments were made on animals in which the cord had 
been divided at the level of the third cervical vertebra. In five 
cases a simultaneous record of the volume of either the kidney or 
the spleen was obtained, and in nearly every case the condition 
of the respiration was recorded at the same time by connecting 
the trachea with a Marey’s tambour and writing lever. The 
records were taken on a Hering’s kymograph. In those experi- 
ments which lasted many hours a continuous record was not taken, 
ee the kymographion was stopped, and set going again for a few 
minutes at intervals of fifteen or thirty minutes, or less as occasion 
demanded, 
: The general features of the blood pressure record following the 
intravenous injection of Pseudechis venom are the same as those 
ies : ee 
esc Y of the results of previous experimenters with snake poisons 
vitiated by their ignorance of this possibility. 
