MORBID POISONS. 351 



action of each respectively are considered more 

 closely, it will in reality be seen that their influence- 

 depends upon the same cause. 



In dry air, and in the absence of moisture, all 

 these poisons remain for a long time unchanged ; 

 but when exposed to the air in the moist condition, 

 they lose very rapidly their peculiar properties. 

 In the former case, those conditions are afforded 

 which arrest their decomposition without destroying 

 it ; in the latter, all the circumstances necessary for 

 the completion of their decomposition are pre- 

 sented. 



The temperature at which water boils, and contact 

 with alcohol, render such poisons inert. Acids, 

 salts of mercury, sulphurous acid, chlorine, iodine, 

 bromine, aromatic substances, volatile oils, and par- 

 ticularly empyreumatic oils, smoke, and a decoction 

 of coffee, completely destroy their contagious pro- 

 perties, in some cases combining with them or 

 otherwise effecting their decomposition. Now all 

 these agents, without exception, retard fermenta- 

 tion, putrefaction, and decay, and when present in 

 sufficient quantity, completely arrest these pro- 

 cesses of decomposition. 



A peculiar matter to which the poisonous action 

 is due, cannot, we have seen, be extracted from 

 decayed sausages ; and it is equally impossible to 

 obtain such a principle from the virus of small-pox 

 or plague, and for this reason, that their peculiar 

 power is due to an active condition recognisable 



