1877.] 



Putrefactive and Infective Organisms. 



233 



to the introduction of the hay which produced the dust, no difficulty as 

 regards sterilization had ever been experienced ; subsequent to its in- 

 troduction my difficulties and defeats began. 



I have twice glanced at periods of boiling amounting to two hundred 

 minutes ; for, after long and laborious trials of shorter periods I advanced 

 to longer ones, subjecting turnip and cucumber infusions to the boiling 

 temperature for intervals varying from five minutes to three hundred and 

 sixty minutes. Up to a certain point these liquids maintained their power 

 of deve]oping life, but beyond this point complete sterility was the result. 

 In the preli min ary experiments bearing upon this question the point of 

 sterilization lay between 180 and 240 minutes. Eoiled for the former 

 period the infusions continued fruitful ; boiled for the latter period they 

 remained permanently barren. 



In these and numerous other experiments a method was followed which 

 had been substantially employed by Spallanzani and Needham, and more 

 recently by Wyman and Eoberts, the method having been greatly refined 

 by the philosopher last named. The flasks were partially filled with 

 the infusions, the portions unoccupied by the liquids being taken up with 

 ordinary unfiltered air. Xow as regards the death-point of contagia 

 we know that in air it may be much higher than in water, the selfsame 

 temperature being fatal in the latter and sensibly harmless in the former ; 

 hence my doubt whether, in my recent experiments, the resistance of the 

 contagium did not arise from the fact of its being surrounded, not by 

 water but by air. 



I changed the method, and made a long series of experiments with 

 filtered air. They were almost as unsuccessful as those made with 

 ordinary air. From time to time I succeeded in producing complete 

 sterility by five minutes' boiling ; but these successes were so checked by 

 failures that, similar to other cases referred to, they appeared in the light 

 of accidents. They were, however, by no means uninstructive, for they 

 revealed the existence of breaks in the prevalence of the contagium, which, 

 under the circumstances, might have been foreseen. 



A rapid glance at the means employed to improve the method of 

 experiment, and at the results of their employment, may be permitted 

 here. Bulbs, exhausted by an air-pump and afterwards heated almost 

 to redness, were filled when cool with filtered air. While being 

 charged with the infusions the bulbs were warmed, so as to produce a 

 gentle outflow of air, and their necks were sealed while the outflow con- 

 tinued. It was thus sought to avoid the contamination consequent on 

 an indraught. 



The failures resulting from this mode of experiment greatly predo- 

 minated over the successes. 



Employing similar bulbs, their necks in the first instance were drawn 

 out at the ends to tubes of capillary fineness. The bulbs were then filled 



