100 



aceti was not, for instance, the aerobic mucor of a ferment 

 differing from it physiologically, say of the lactic ferment, 

 whose analogies of form with the Mycoderma aceti are 

 sometimes striking. I have not found anything hitherto. 

 What I deny, with reference to this Mycoderma, are the 

 polymorphisms admitted by M. Bechamp and other authors, 

 which, in my judgment, rest upon erroneous and incomplete 

 observations." Dr. Miquel, whose remarkable book on " Les 

 Organismes Vivants de 1' Atmosphere," containing the record 

 of his experiments at the Montsouris Observatory, is full of 

 interest, gives his testimony on the same side. " The theory 

 of the evolution of species," he says, " can derive little profit 

 from this class of experiments if they are conducted witli 

 the necessary rigour." After an enormous number of experi- 

 ments he has found that the different species of microbes 

 maintain their ha.bits and their individuality unchanged for 

 months and years. "Of 80,000 experiments," adds Dr. Miquel 

 elsewhere, "not one has contradicted the aflBrmations of M. 

 Pasteur, while many are in complete opposition to the 

 statements published by some of his too zealous or inexperi- 

 enced followers." Klein, as well as Koch, has also been forced 

 to the conclusion that no satisfactory proof of the truth of 

 Von Nageli's fascinating hypothesis of the "sporting" of 

 saprophytes, or in other words, of the conversion of patho- 

 genic bacteria into harmless saprophytes, and the reduction 

 of the latter into the former, has yet been adduced, and he 

 has published a series of experiments tending to show that 

 Buchner was mistaken in supposing that he had established 

 the convertibility of Bacillus suhtilis and Bacillus anthra- 

 cis, and offering an explanation of the phenomena on which 

 Buchner's conclusion was based. 



11. — Nevertheless it must be admitted that the successive 

 outbreaks and disappearances of epidemics, and the observa- 

 tions of Pasteur and others on the adaptability of microbes 

 to different environments, and on the attenuation and 



