CHAPTER XIV. 
NEUROTOXINS OF SNAKE VENOM. 
Through the exhaustive investigations of early physiologists and patholo- 
gists, notably of S. Weir Mitchell, Reichert, Fayrer, Brunton, Wall, Ragotzi, 
C. J. Martin, and Calmette, and of those of more recent date, Kyes, Lamb, 
Fraser, Elliot, Rogers, Flexner and Noguchi, Stephens, Myers, Noc, and others, 
it has been established beyond doubt that snake venom contains, besides 
many other toxins, a definite, independent principle which has a specific 
destructive action upon the nervous system, the neurotoxin. All evidences 
brought out either by direct clinical or by experimental observations point to 
the fact that neurotoxin plays the most important part in producing the death 
of the victims of venom poisoning. As has already been pointed out elsewhere, 
the venom fibrin ferment and hemorrhagin can also be primary factors in 
producing the fatal issue or venom toxication, yet these are not distributed as 
widely as the neurotoxin and are present only in certain viperine and a few 
colubrine snake venoms, in such paramount proportions as to form the prin- 
cipal fatal constituent of these venoms. 
The neurotoxin is the chief death-dealing agent of the venoms of all poison- 
ous Colubridze and is present in these venoms in enormous amounts; the 
venoms of Viperide contain it in comparatively small quantities, while those 
of the Hydrophide are richest of all in this principle. It is noteworthy that 
the chief toxic principles of the Viperidz and of a few of elapine Colubride 
consist of blood-clotting ferment and hzmorrhagin, and the neurotoxin is of 
subordinate importance. 
Numerous nervous symptoms produced by the injection of different snake 
venoms convinced most of the investigators of the presence of neurotic toxins in 
the venoms. It was perhaps Weir Mitchell who first established the complex 
nature of snake venom and pointed out that there existed in venom at least 
two distinct sets of poisonous principles, one acting chiefly upon the nervous 
system, the other causing extensive local lesions. Fayrer and Brunton paid 
special attention to the importance of neurotoxins and concluded that the 
direct cause of death from venom poisoning is the same with all kinds of 
venoms and is the result of the action of the venom upon the nervous tissues. 
They thought that the neurotoxins are also present in large quantities in the 
venoms of Daboia, Pseudechis, Notechis, and Crotalus. Wall ascribed the 
rapid death from daboia poisoning to the presence of a neurotic principle 
with special elective action upon the center of convulsion. As will presently 
be seen, this neurotic theory of Wall on daboia poisoning has been completely 
overthrown by later investigators, especially by Lamb, who demonstrated 
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