NATURE OF SNAKE VENOM. 355 
venom of only one species of snake fails to act as a sufficiently 
satisfactory antidote in all forms of snake bite. 
The difference in the constituents of venom is so great that 
the venom of each species of snake differs in its action, even with 
those belonging to the same genus. For instance, the serum of 
an animal rendered immune to the bite of a Cape Cobra (Nava 
flava) proved on experimentation to be an antidote to the bite 
of this particular species of snake, but only had a partial antidotal 
effect upon the venom of another species of Cobra, nearly double 
the dose being necessary to neutralize the venom injected. 
Tested on animals bitten by Puff Adders, or injected with fatal 
doses of their venom, this serum had very little curative power. 
The poisonous substances in snake venom may be separated 
into three main parts. 
(1) NEUROTOXINS, or nerve poisons. These combine with the 
nerve cells and paralyse them. Neurotoxins are present in all 
venoms, but are most potent in the poison of the Cobra. 
The nerve poisons, of some species of snakes, will cause 
paralysis of the nerve centres controlling the breathing, resulting 
in collapse of the lungs. Each variety of nerve poison acts with 
greater or lesser power upon the various groups of nerve centres, 
according to its nature. The nerve poison in one species of 
snake will cause complete paralysis of a certain set of nerve 
centres, while the nerve poison of another kind of venom will 
have little or no poisonous effect upon that particular nerve 
centre, but will concentrate its benumbing power on‘a group of 
nerve cells which the former venom has either not affected at 
all, or only to a slight degree. 
In severe cases of Cobra poisoning, a certain amount of 
structural change takes place in the nerve cells, numbers of them 
being broken up and destroyed. However, death is not usually 
caused by wholesale destruction of nerve cells, but by the para- 
lyzing action of the neurotoxin upon the cells. This neurotoxin 
is strong in Cobra venom. 
(2) H@&MORRHAGINS, or blood poison. This portion of the 
venom acts upon the endothelial cells, phagogytes, and red 
corpuscles of the blood. The endothelial cells are the cells of 
a membrane which lines the inside walls of blood vessels. The 
cells are thin and flat. The venom alters their shape, changes 
and expands their structure sufficiently to allow the altered 
