14 DE. BASTIAN OK THE 



and swarm with organisms even at this comparatively low tempera- 

 ture. When subjected to a high temperature (122" F.), these 

 previously boiled neutral infusions will still more frequently fer- 

 ment, though this very strong stimulus will (as we have seen) 

 also cause some otherwise barren acid infusions to ferment and 

 swarm with organisms. 



In the summer of 1875 I first made experiments with urine to 

 ascertain whether it followed the rule above alluded to — that is, 

 whether, like other acid fluids, its fermentability would be in- 

 creased by previously neutralizing it with liquor potassse. This 

 preliminary inquiry was soon answered in the affirmative. 



Then came the more important question as to the cause or 

 mode of production of such increased fermentability. Tor two 

 reasons urine seemed to me to be a fluid specially favourable for 

 use in attempting to throw light upon this problem: — -Jlrsf,heca.u8e 

 of the unanimity of experimenters as to the fact that, when boiled 

 in its acid state and subsequently guarded, it invariably remained 

 barren *; and secondly, because the marked acidity of urine would 

 necessitate the use of liquor potassae in easily measurable quanti- 

 ties, even when providing for the neutralization of such small por- 

 tions of fluid as are commonly employed in these experimentsf . 



Two alternative views are possible as to the cause of the 

 fact in question : — (1) It may be due to the " survival of germs " 

 of some of the ferment-organisms in the boiled neutral infu- 

 sions, as Pasteur asserts ; or (2) it may be due to the mere 

 chemical influence of potash in initiating and favouring the 

 molecular changes leading to fermentation, as originally sug- 

 gested by Gerhardt. 



This important question would seem to be so capable of being 

 settled by crucial experimentation as to make it not a little re- 

 markable that no such attempt was ever made by M. Pasteur. 

 Thus, the fluids may be boiled in their acid state so as to kill all 

 their contained germs and organisms, and to these fluids boiled 

 liquor potassge may be added in suitable quantity +. The results 

 of a number of such experiments should be sufficiently decisive to 



* This was my own experience also at the time. It was not till a later period 

 that I began to obtain the results with high incubating temperatures, which have 

 already been recorded (p. 7). 



t Mostly from 1 to 1^ fluid-ounce has been made use of by me. 



\ A few experiments of this nature were first made by Dr. William Eoberts 

 with hay-infusion (Phil. Trans. 1874, vol. clxiv. pt. 2, p. 474). 



