124 MICROBES, FERMENTS, AND MOULDS. 
both in air and water may, therefore, be indefinitely 
preserved in a protective medium, such as a brick 
wall covered with plaster. They are nourished at 
the expense of the ammoniacal salts which are found 
in the air in a gaseous state, and which are fixed by 
atmospheric moisture, and it is probable that they 
derive little nutriment from the solid materials in 
the midst of which they live, although by their 
increase disintegration may ensue. Hence, especially 
from the hygienic point of view, it is so important to 
disinfect the walls of hospitals, barracks, stables, etc., 
by scraping and whitewashing them. 
Parize also believes that microbes may perform 
a geological part in nature by disintegrating the 
schistoid rocks which enter into the constitution of 
arable soil. But we are now speaking of microbes of 
recent origin, since the temperature to which clay is 
subjected in order to make red bricks would certainly 
destroy all the microbes and their germs. This is not 
the case with the microbes of chalk, which, according 
to Béchamp, are of very ancient origin. 
XIII. THe Microses oF CHALK AND COAL. 
Béchamp’s researches tend to show that microbes, 
which he calls microzyma, or small ferments, have an 
almost indefinite term of life. We know that chalk 
consists almost entirely of the remains of the calcareous 
