158 MICttOBES, FERMENTS, AND MOULDS. 



Schizophyta may therefore have two very different 

 modes of existence, comparable to the hetersecia (change 

 of habitat) and dimorphism of the fungi Ascomycetes 

 and Basidiomycetes. Schizomycetes however, although, 

 like fungi, they obtain their nourishment from organic 

 substances which have been already elaborated, are 

 not true parasites in the first stage of their existence, 

 during which stage they live freely in the water, or on 

 the damp soil. They become true parasites when they 

 penetrate into the blood and tissues of man, in which 

 they necessarily live at the expense of their host. 



Hence it may be seen why half-dried marshes, 

 meadows from which a river has retreated in order 

 to return to its bed, great excavations of the soil 

 necessary in railway-cuttings, etc., become the source 

 of a large number of epidemic or contagious diseases. 

 In all these places the subsiding waters have left 

 Schizopkyta, or microbes in a dried state, and these 

 are soon transformed into dormant spores, which are 

 diffused through the air and enter the mouth and 

 lungs of men living near the rivers and marshes, or 

 who are working on the railway-cutting. The soil 

 which has remained undisturbed for a long while is 

 full of dormant spores, drawn into it by the rain to 

 a greater or less depth; these may preserve, their 

 vitality for many years, waiting for the favourable 

 medium which leads to their fresh development. 



An acquaintance with air-germs, with the microbes 

 of earth and water, has therefore become indispensable 



