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PROGRESS OF MICROSCOPICAL SCIENCE. 
Ardwick, at Manchester, and which appears to have been a double 
seed, resembling in general form the samara of an ash. It belongs to 
lirongniart's genus Polypterosjpermum. 
M. Pasteur's Meply to Dr. Bastian on the Heterogeny Controversy. — 
The ' Lancet ' of August 5 has the following interesting note on the 
above subject : — A communication recently made by Dr. Bastian to 
the Paris Academy of Sciences, upon the influence of physico-chemical 
forces upon the phenomena of fermentation, has met with a prompt 
reply from M. Pasteur,* in a note on the changes undergone by 
urine, in which he points out what he considers to be errors in 
Dr. Bastian's experiments, which he has himself repeated. In his 
opening remarks, he contrasts the supporters of spontaneous genera- 
tion with the theorisers in physics and mathematics who believe in 
perpetual motion or in the quadrature of the circle ; and he thinks that 
the only reason why heterogenists are listened to at all is because of 
the impossibility of proving a priori the origin of life except from 
life — in other words, because biology is not yet an " exact " science. 
Turning to Dr. Bastian's paper, he singles out for especial comment 
those experiments in which bacteria appear in urine mixed with oxygen 
and solution of potash, and kept at a temperature of 122° F. (50° C), 
the urine having been previously boiled, and all precautions taken to 
withdraw it from any source of contamination by atmospheric germs. 
M. Pasteur admits that Dr. Bastian's experiments are very exactly 
carried cut, but he contends that a temperature of 50° C. is not suffi- 
cient to kill all the germs of minute organisms which may be intro- 
duced into the urine by means of the solution of potash. In his 
memoir, published in 1862, and entitled ' Sur les Corpuscles organises 
qui existent dans I'Atmosphere : examen de la doctrine des Genera- 
tions Spontanees,' he showed that acid liquids which are rendered 
sterile after a few minutes' exposure to a temperature of 100° C. 
remain fertile when made slightly alkaline ; and he considers the 
precaution adopted by Dr. Bastian, of further heating the fluid to 50°, 
to be superfluous. He considers it fully proved that the germs of 
certain organisms which do not resist a temperature of 100° in acid 
solutions, are capable of such resistance in neutral or slightly alkaline 
fluids. In the latter case, in order to effectually destroy all germs, 
the solutions must be heated above boiling point — e. g., to 110° C. He 
therefore recommends Dr. Bastian to repeat his experiments with the 
additional precaution of adding solid caustic potash previously heated 
to redness or to a temperature of 110°, instead of employing the 
alkali in aqueous solution ; or simply to heat the urine and liquor 
potassse to 110° instead of 100°. M. Pasteur has found that per- 
fectly normal urine rendered alkaline by a piece of solid potash 
undergoes no change when due precautions are taken to get rid of the 
contact of the atmospheric germs; and, in conclusion, he expressed 
the hope that Dr. Bastian would abandon his faith in spontaneous 
generation and in the proofs which he thinks he has given of it. At 
the same meeting M. Pasteur related observations showing that the 
* * Comptes Rendug,' July 17. . 
