THE BACTERIA IN DIFFERENT MEDIA. 143 



then, to be a secretion of the Micrococcus urece; 

 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 

 group 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 urece, leaving the field 

 free to other organisms capable of living 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 



