REPTILES. 



strong tendency to rapid putrefaction. 3. Although Dr. 

 Mead^mingled the venom of a viper with healthy blood out 

 of the body, without perceiving it to produce any change in 

 its appearance, this arose from his mixing a very small por- 

 tion of poison with a large portion of blood ; but if two or 

 three drops of venom be mixed with forty or fifty drops of 

 blood, it immediately loses its vermilion colour, becomes 

 black, and is incapable of coagulation. 4. It is, moreover, 

 a remarkable circumstance, that the poison of serpents has 

 most power over those animals whose blood is the warmest, 

 and the action of whose heart is the most lively ; whereas, 

 on the contrary, it is but a feeble poison to the serpent 

 itself, and a very tardy instrument of death to most cold- 

 blooded animals. The reason of this, according to Mr. 

 Boag, appears to be, that cold-blooded animals do not re- 

 quire a large quantity of oxygen to preserve their lives ; 

 and this is indeed evident from the conformation of their 

 heart and respiratory organs. 



Fontana's experiments, with a view to the prevention of 

 the fatal effects of poisons, may be stated in a few words. 

 He applied lunar caustic, which is a preparation of sdver 

 in nitric acid, and found, on so doing, that not only was the 

 venom thereby rendered innocuous, but that the corroding 

 power of the caustic was greatly diminished. He next 

 wounded a variety of animals, by means of envenomed 

 teeth, and scarifying the wounds, he washed them in a so- 

 lution of lunar caustic and water : by this means the lives 

 of the greater number of the animals were saved, though 

 they befoncred to species which he knew, in general, to be 

 mosi easilv killed, and the death of the others was greatly 

 retarded. ' These experiments, we may add, neither pro- 

 ceeded upon nor conducted to any theory. 



Now, the applic:ilion of the following admitted facts is 

 supposed by Mr. Boag to explain the efficacy of Fontana's 

 treatment, and illustrates the accuracy of his own views:— 

 1. Oxygen enters into the composition of all acids, and is 

 the principle, as its name imports, upon which their acidity 

 depends. 2. Metals are united with oxygen under various 

 circumstances, but chiefly in two ways; the first is by 

 burning them in an open fire, or, to speak more philo- 

 Bophicaily, bv the contact of heat and air, when they are 

 converted into metallic oxides ; the swond is l)y the decom- 



H 2 



