36o THE SNAKES OF SOUTH AFRICA. 



Cobras and Mambas are far more to be dreaded than Vipers 

 because their venom acts so rapidly on the nerve centres, often 

 causing death or reducing the person bitten to a condition im- 

 possible of recovery before there is time to apply any remedial 

 measures. 



However, the venoms of all snakes of the Colubrine family do 

 not act in this rapid way upon the nerve-centres in the brain 

 and medulla. The venoms of many act primarily on the blood 

 and secondarily on the nerve centres, as for instance in the case 

 of the Boomslang, which is a member of the Colubrine family, 

 although in classification it is placed in a sub-family with other 

 back-fanged snakes. 



When a dose of viper venom is injected into a vein, even if 

 the quantity be small, death rapidly results from clotting of the 

 blood, chiefly in the pulmonary arteries. In animals, if a small 

 fraction of a drop is injected direct into a vein, death quickly 

 follows from clotting of the blood caused by a poisonous principle 

 in the venom known as Fibrin-ferment. 



In these cases no remedial measures arc of any avail. 

 The venoms of the different species of snakes differ con- 

 siderably in the blending of the nerve poisons (neurotoxins), 

 blood poisons (haemorrhagins), and blood-clotting poison (Fibrin- 

 ferment). This being so, the symptoms vary more or less 

 widely. The venoms of two different species of snakes which 

 apparently produce the same outward physiological effects are 

 found, when examined, to be more or less dissimilar in their 

 composition. However, when the victims are subjected to 

 post-mortem it will be discovered that the venom of one snake 

 has produced internal effects considerably different from the 

 other. 



The venoms of the Colubrine (Cobra) family of snakes and 

 the Viperine (Adder) family differ most widely in their nature 

 and effects. Generally speaking, we can say that the venom 

 of the typical Cobra family of snakes acts rapidly and chiefly on 

 the nerve-centres, causing nerve paralj-sis and death ; while the 

 venom of the Adders, although causing severe nerve depression, 

 exerts a powerful poisonous influence on the blood and walls of 

 blood vessels. 



Snake venom, when mixed with ammonium sulphate or 

 absolute alcohol, causes the poisonous substances (proteids) to 



