238 TROPICAL MEDICINE AND HYGIENE 



individual and its condition at the moment whether 

 fresh or exhausted, fasting or full, long captive or new- 

 taken, &c. In experimental work the amount is estimated 

 by carefully drying and weighing the secretion obtained 

 by firm pressure on the glands of the living snake. Major 

 Lamb estimates that a cobra of middle size will thus 

 yield about 200 mgm. of dried venom, sufficient to kill 

 eight average men. 



Physical and Chemical Characters of Venom. Snake- 

 venom is a clear (sometimes opalescent), slightly viscid 

 fluid of a yellow colour ; it is odourless, tasteless (some- 

 times bitter), of a very high specific gravity, and in 

 normal reaction acid. It is rich in soluble proteids, and 

 it is to these, as was first demonstrated by Weir Mitchell 

 in 1874, that it owes its virulence. Some of these 

 proteids notably those that predominate in the venom 

 of Viperidce are coagulated and impaired in power by 

 heat short of boiling point, and are destroyed by gastric 

 juice. Others notably those that predominate in the 

 venom of Colnbridce are not. All, however, are destroyed 

 by prolonged boiling and by pancreatic juice. 



Snake-venoms give the usual proteid reactions, and are 

 rendered inert by the various chemical reagents e.g., 

 strong caustics, and strong oxidizing agents like per- 

 manganate of potash and hypochlorite of lime that 

 destroy proteids or precipitate them from solution. They 

 can be dried in the usual ways. Dried venom breaks 

 into lumps, or flakes, or needles, like gum-arabic or 

 lodoform. When properly dried it keeps indefinitely ; 

 it dissolves again readily in saline solution or water, and 

 the solution is fully potent. 



Nature and Action of Venom. From the biological 

 standpoint it is safe to regard snake-venom as essentially 

 part of the digestive mechanism ; to an animal that 

 swallows relatively enormous prey with integuments 

 practically intact, it must be a crucial advantage to be 

 able to impregnate the. prey with powerful ferments and 

 solvents. 



