Pathogenic 3Iicrobcs in the Static Condition. 43 



disease is bound to the soil : paliidic fevers, perhaps 

 yellow fever. 



The three classes of germs which we have just been 

 considering explain the distinction formerly made be- 

 tween the different forms of virus. The first corre- 

 sponds to contagions, the second to miasmatic-contagions, 

 and the third to the miasms j^roj^erly so called. 



Usually we also class with the miasms the toxic 

 gases which are disengaged from cesspools, and the 

 poison of the expired air. 



Baumgarten has divided pathogenic microbes into 

 exogenous and endogenous, according to whether they 

 come from the exterior or from the diseased subjects 

 themselves. 



II. Distribution of ^pathogenic germs. 



A certain number of pathogenic germs are ubiquit- 

 ous in nature; we meet with them almost every- 

 where. Such is the case with the germs of suppura- 

 tion and of septicsemias, on account of their excessive 

 production and the readiness with which they live in 

 the surrounding media. Specific germs are only in- 

 cidentally found in such media. 



In the following lines we will review in succession 

 the various media which may contain germs noxious 

 for the economy, this study being essential to a cor- 

 rect understanding of the diflferent methods of con- 

 tagion. 



Air. — We have seen, in the first part, that the air 

 can hold germs in suspension ; it is natural to think 

 that among these we may find some which are pos- 

 sessed of pathogenic properties. Moreover, it can 

 readily be understood that the dust of the streets 



