376 POISONS, CONTAGIONS, MIASMS. 



become covered with water containing a certain 

 quantity of this matter in solution. This water 

 soon becomes turbid, and in common language 

 putrefies, or, to describe the change more correctly, 

 the state of decomposition of the dissolved conta- 

 gious matter is completed in the water. 



All gases emitted from putrefying animal and 

 vegetable substances in processes of disease, gene- 

 rally possess a peculiar nauseous offensive smell, a 

 circumstance which, in most cases, proves the 

 presence of a body in a state of decomposition. 

 Smell itself may in many cases be considered as a 

 reaction of the nerves of smell, or as a resistance 

 offered by the vital powers to chemical action. 



Many metals emit a peculiar odour when rubbed, 

 but this is the case with none of the precious 

 metals, those which suffer no change when exposed 

 to air and moisture. Arsenic, phosphorus, musk, 

 the oils of linseed, lemons, turpentine, rue, and 

 peppermint, possess an odour only when they are 

 in the act of eremacausis (oxidation at common 

 temperatures). 



The odour of gaseous contagious matters is owing 

 to the same cause ; but it is also generally accom- 

 panied by ammonia, which may be considered in 

 many cases as the means through which the con- 

 tagious matter receives a gaseous form, just as it 

 is the means of causing the smell of innumerable 

 substances of little volatility, and of many which 

 have no odour. (Robiquet.)* 



* Ann. de Chim. et de Phys. XV. 27. 



