3S4 POISONS, CONTAGIONS, MIASMS. 



therefore enters into combination with parts of the body, or causes 

 their decomposition, it is termed'MiASM. 



Gaseous contagious matter is a miasm emitted from blood, and 

 capable of generating itself again in living blood. 



But miasm, properly so called, causes disease without being 

 itself reproduced. 



All the observations hitherto made upon gaseous contagious 

 matters prove, that they also are substances in a state of decom- 

 position. When vessels filled with ice are placed in air impreg- 

 nated with gaseous contagious matter, their outer surfaces 

 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 process of decomposition of the dissolved contagious 

 matter is completed in the water. 



All gases emitted from putrefying animal and vegetable sub- 

 stances in processes of disease, generally possess a peculiar 

 nauseous offensive smell, a circumstance which, in most cases, 

 proves the presence of a body in a state of decomposition, that is, 

 of chemical action. Smell itself may, in many cases, be con- 

 sidered 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 odor when rubbed, but this is the 

 case with none of the noble metals,. — those which suffer no 

 change when exposed to air and moisture. Arsenic, phos- 

 phorus, musk, the oil of linseed, lemons, turpentine, rue, and 

 peppermint, possess an odor only when they are in the act 

 of eremacausis (oxidation at common temperatures). 



The odor of gaseous contagious matters is owing to the same 

 cause ; but it is also generally accompanied by ammonia, which 

 may be considered, in many cases, as the means through which 

 the contagious 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 odor. (Robiquet.)* 



Ammonia is very generally produced in cases of disease ; it is 

 always emitted in those in which contagion is generated, and is 



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



