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 haemorrhagin 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 Colubridae and is present in these venoms in enormous amounts; the 

 venoms of Viperidae contain it in comparatively small quantities, while those 

 of the Hydrophidae are richest of all in this principle. It is noteworthy that 

 the chief toxic principles of the Viperidse and of a few of elapine Colubridae 

 consist of blood-clotting ferment and haemorrhagin, 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 



143 



