DEVELOPMENT OF THE BACTERIA. LOE 
is the first question which presents itself,—a ques- 
tion which has given rise to long discussions, in 
the examination of which we shall only enter in 
order to give a short historical statement. 
§ 1.— OriGIN OF THE BAcTERIA. 
The origin of the bacteria, as of all the other 
inferior organisms, 1s conceived in three different 
manners : — 
1. For some, these organisms are produced by 
heterogenesis ; that is to say, by creation outright 
from mineral-or organic substances (spontaneous 
generation), 
2. According to others, they come directly from 
individuals like themselves, by one of the known 
modes of generation, — fission, spores, ete. 
3. Finally it 1s believed that they are derived 
from organisms already existing, and are nothing 
more than different states or phases of develop- 
ment of known species, of which the life cycle is 
not yet discovered. 
We will examine the latter hypothesis, which 
constitutes what is called polymorphism, when we 
speak of the phenomena of reproduction. 
As to the two first, we will content ourselves 
with indicating the late works which have appeared 
for and against each; insisting above all upon the 
facts which relate to the proof of the presence of 
bacteria or their germs in the air, water, and 
liquids or tissues of the human organism, — blood, 
urine, ete. 
