326 APPENDIX. 



date. The scientific mind will not halt in its decision 

 between these two alternatives. 



For my own part the gradual but irresistible interaction 

 of thought and experiment made it in the first instance 

 probable, and at last certain, that the atmosphere in which 

 I worked had become so virulently infective as to render 

 utterly impotent precautions against contamination and 

 modes of sterilization which had been found uniformly 

 successful in a less contaminated air. I therefore removed 

 from the laboratory, first to the top, and afterwards to the 

 basement of the Royal Institution, but found that even 

 here, in a multitude of cases, failure was predominant, if 

 not uniform. This hard discipline of defeat was needed to 

 render me acquainted with all the possibilities of infection 

 involved in the construction of my chambers and the treat- 

 ment of my infusions. 



I finally resolved to break away from the Royal 

 Institution, and to seek at a distance from it a less infec- 

 tive atmosphere. In Kew Gardens, thanks to the President 

 of the Royal Society, the requisite conditions were found. 

 I chose for exposure in the Jodrell laboratory the special in- 

 fusions which had proved most intractable in the laboratory 

 of the Royal Institution. The result was that liquids which 

 in Albemarle Street resisted two hundred minutes' boiling, 

 becoming afterwards crowded with organisms, were utterly 

 sterilized by five minutes' boiling at Kew. 



A second clear issue is thus placed before the Royal 

 Society: — Either the infusions had lost in Kew Grardens 

 an inherent generative energy which they possessed in our 

 laboratory, or the remarkable instances of life- development, 

 after long- continued boiling, observed in the laboratory 

 are to be referred to the contagium contained in its vessels 

 or difiused in its air. 



With a view to making nearer home experiments similar 

 to those executed at Kew, I had a shed erected on the roof 

 of the Royal Institution. In this shed infusions were 

 prepared and introduced into new chambers of burnished 

 tin, which had never been permitted to enter our labora- 



