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THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



change even when kept in moderate incubating 

 temperatures ; while there was one preparation, 

 viz., a strong infusion of turnip with a little 

 cheese-dust added, which was almost certain to 

 develop life. 



Not only did different substances behave thus 

 differently, but for some inscrutable reason the very 

 same infusion would often give negative results 

 if diluted, when it seldom failed, if concentrated, 

 to undergo putrefactive change with its regular 

 accompaniment of bacterial life. By degrees, too, 

 Dr. Bastian found out that infusions which re- 

 mained sterile at such low incubating tempera- 

 tures as 70° or 80° Fahr. would often yield to the 

 more genial influence of greater warmth, and that 

 even the most intractable would in some instances 

 succumb to a temperature from 115° to 122°. 

 The importance of this last element in the pro- 

 cess was not as fully ascertained as it is now till 

 after Dr. Sanderson's investigation, but recent ex- 

 periments have shown that specimens of even so 

 resistant a fluid as urine, when not too decidedly 

 acid, are sometimes capable of producing life if 

 kept, after boiling and sealing, in a bath at a 

 temperature of 122°. No general rule can yet be 

 laid down by which the behavior of any particu- 

 lar fluid may be certainly predicted from its con- 

 stitution without actual trial, but Bastian's re- 

 sults agreed in the main with many older obser- 

 vations to the effect that neutral or very faintly 

 alkaline fluids would putrefy after boiling and 

 sealing more frequently and readily than acid in- 

 fusions. Bastian has also made the further dis- 

 covery that fertility might be prevented as much 

 by excess of alkali as by excess of acid, and that 

 some infusions were almost always sterile unless 

 exact neutralization was secured. Notwithstand- 

 ing this approach to a generalization, he obtained 

 positive results in many instances from acid, from 

 neutral, and from alkaline fluids. We may add 

 that he found (as Spallanzani and other observers 

 on both sides of the question had long before 

 done) that with most fluids a great increase in 

 the duration of the boiling was adverse to the 

 subsequent evolution of life, sometimes retarding 

 its appearance for many days, and sometimes 

 preventing it altogether ; though at the same time 

 he ascertained that the action of other infusions 

 was less easily interfered with, and that some 

 would putrefy notwithstanding exposure to a boil- 

 ing heat for one or more hours. Increase of tem- 

 perature, and, according to some observers, even 

 a small increase beyond the boiling-point, has 

 also been proved to check life-development, al- 

 though instances are recorded of putrefaction 



after exposure to such considerable temperatures 

 as 110°, 125°, and even 150° C. 



The discussion of the inferences to be drawn 

 from cases of excessive or prolonged heating will 

 be better deferred until we come to consider the 

 whole mass of evidence on the question of the 

 amount of heat required to destroy life in bacte- 

 ria or their germs, if germs they have. At this 

 stage we shall confine ourselves to cases where 

 the temperature was that obtained by boiling 

 maintained for a few minutes only. 



"When these experiments were published in 

 1871 and 1872, the scientific world naturallv 

 hesitated to accept them finally without con- 

 firmation, the more especially as they were of a 

 kind that called for very careful manipulation, 

 and pointed to a conclusion opposed to what was 

 then the prevalent opinion on the subject. Among 

 those who had expressed their doubts as to the 

 accuracy of Bastian's work was Dr. Burdon-San- 

 derson. To set the matter at rest a series of fif- 

 teen flasks were operated upon in his presence 

 according to Bastian's method. 



Of these one was rejected in consequence of 

 having become cracked, and of the remaining 

 fourteen ten putrefied and produced bacteria 

 and other forms of life, while four remained for 

 several days, and perhaps, if not then broken for 

 observation, would have remained permanently 

 pure. Of the ten infusions which produced life, 

 two were infusions of hay, one a strong infusion 

 of turnip in its naturally acid state, two similar 

 infusions of turnip neutralized with potash, two 

 turnip with cheese, and three the same neutral- 

 ized. 



All the vigilance of an observer as acute and 

 experienced as Dr. Sanderson failed to detect the 

 slightest flaw in these experiments ; and he frank- 

 ly and publicly declared that he had been mis- 

 taken in his previous doubts, and that it was 

 established to his satisfaction that infusions can 

 be prepared which are not deprived, by an ebul- 

 lition of from five to ten minutes, of the faculty 

 of undergoing those chemical changes which are 

 characterized by the presence of swarms of bac- 

 teria, and that the development of these organ- 

 isms can proceed with the greatest activity in 

 hermetically-sealed jglass vessels from which al- 

 most the whole of the air has been expelled by 

 boiling. 



While this important test was being applied 

 to Bastian's work, Profs. Huitzinga, of the Uni- 

 versity of Groningen, and Cohn, of Breslau, and 

 other well-known savants, had been occupying 

 themselves with similar investigations, and immc- 



