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incessant activity, one of the greatest forces which govern matter and 
determine its transformations. In applying all the faculties of his 
deeply investigating mind to the study of these infinitely small beings, 
much more powerful than the antediluvian monsters and often much 
more dangerous, M. Pasteur has succeeded in watching them at work 
in catching the play of their functions and in establishing their relations 
to the phenomena of fermentation of which they are necessary agents. 
These micro-organisms swarm by millions in the atmosphere. 
They lie everywhere ; our clothes, our furniture, our books, the walls, 
the hangings of our houses are covered with them. The water we use 
for our ablutions, the water which purifies, as we fancy, the things it 
washes, the water we drink, how many microbes does it not contain and 
nourish ? Miguel has demonstrated that a single glass of Seine water 
contained 300,000 microbes. Evidently, all these micro-organisms are 
not malefactors : many of them are, on the contrary, for us very useful 
auxiliaries, others are quite harmless or indifferent. But mixed with 
these indifferent germs, there exists around us an immense quantity of 
them which are formidable. Such are the germs of infectious and con- 
tagious diseases, especially during epidemics. 
These ferments, introduced with food into our stomach, feed them- 
selves upon what we have prepared for our own nutrition ; they are our 
guests, our parasites, and live upon the portion of our aliments which 
we do not consume, clients who eat the leavings of the table. A great 
number of them are immediately killed by the chlorhydric acid of the 
gastric juice ; among those remaining some work for us, playing an 
important role in the digestive transformation of alimentary substances, 
but more often they openly work against us. 
It has been thoroughly demonstrated by recent investigations, that 
the pathogruic microbes secrete, by the fact of decomposition produced 
by their vital action, special toxic substances, real nitrogenous bases 
similar to the alkaloids extracted from vegetables, such as quinine, 
morphine, strychnine, which dissolved in the fluids of the organism 
produce a true poisoning. It is they which incessantly fabricate in the 
digestive tube compound ammonia, such as indol, leucin, tyrosin, 
phenol, scatol. Carbonic acid and other gases are set free, such as for 
example, sulphurated hydrogen, and the products secreted by these 
