THE BACTERIA IN DIFFERENT MEDIA. 143 
then, to be a secretion of the Micrococcus uree ; 
and perhaps the role of the bacteria is limited, in 
the phenomena of fermentation, to the formation of 
this secretion alone. The ammoniacal transforma- 
tion of urine would consequently enter into the 
croup of fermentations by the varieties of diastase. 
According to Arnold Hiller, if carbolic acid be 
added to urine, it does not become alkaline; on 
the contrary, the acidity is even augmented, and 
that notwithstanding a considerable number of 
bacteria which develop in it. Has the carbolic 
acid killed the Micrococcus uree, leaving the field 
free to other organisms capable of livmg in an 
acid medium, and of producing other transforma- 
tions of the constituents of the urine? In the 
memoir which we here cite, the author, resuscitat- 
ing the ancient opinion of Liebig, wishes to dem- 
onstrate that the decomposition of dead organic 
matters, and putrefaction in general, are phenom- 
ena purely chemical, — these decompositions being 
determined by the presence of organic substances, 
themselves undergoing transformations. 
We will not stop to consider these views, long 
since refuted: the experiments upon which they 
are founded are easily criticised. It is sufficient 
for me to say that they are in formal opposition 
with all the observations contained in modern 
works upon this question. 
It is especially in relation to ammoniacal fer- 
mentation that the question of spontaneous gen- 
eration has been discussed. We have already 
seen the results arrived at, and will not return to 
