88 ZOOLOGY OF INDIA. 



The extreme rapidity with which death was sometimes 

 produced by the bite of poisonous snakes led Dr. Mead to 

 infer that its fatal influence affected the nervous rather than 

 the circulating system. But the experiments of Fontana 

 go far to demonstrate that the venom of the viper is per- 

 fectly innocent when applied to the nerves only, but that it 

 acts immediately upon the blood, and through .the medium 

 of this fluid destroys the irritability of the muscular fibre, 

 and thus produces death. A more recent idea has been 

 proposed, — that the poison of serpents acts upon the blood 

 by attracting the oxygen which it contains, and which is 

 essential to its vitality. The human heart, and in general 

 the heart of all animals with warm blood, has two cavities 

 or ventricles, and the blood, before it is returned to the right 

 ventricle of the heart, has to perform two circles, a lesser 

 between the heart and the lungs, and a greater between the 

 heart and the rest of the body. While the blood passes 

 through the lungs it undergoes a very remarkable change 

 of colour, and of other properties ; a certain portion of the at- 

 mospheric air is attracted and absorbed, while the remainder 

 carries off by expiration that matter in the blood which is 

 either useless or injurious to the system. The atmosphere we 

 respire is a compound fluid, one portion of which is oxygen, 

 or pure air, and another, and much larger portion, is nox- 

 ious or azotic air ; and it is the former ingredient only 

 which is attracted by the blood in its passage through the 

 lungs, and contributes to the maintenance of animal life. 

 It is from this combination that the heat of animals and 

 the red colour of the blood are supposed to be derived. 



These observations will enable the reader to judge more 

 clearly of Mr. Boag's theorj' of the action of animal poisons. 

 He adduces the following arguments in its support: — 1. 

 Man, and other warm-blooded animals, exposed to an atmo- 

 sphere deprived of oxygen, quickly expire. The poison of a 

 serpent, when introduced into the blood, also causes death ; 

 but carried into circulation by a wound, and in very small 

 quantity, its operation is comparatively slow and gradual. 

 2. The appearances, on dissection, in both cases, are veiy 

 similar. The blood becomes of a darker hue, and coagu- 

 lates about the heart and larger vessels. The irritability of 

 the fibres is nearly, in either case, destroyed to the same 

 degree, and in both circumstances the body exhibits a 



