232 



Prof. J. Tyndall on the Deportment of [^lay 17, 



the infusions had lost in Kew Gardens 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 of its vessels or of 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 Institu- 

 tion. In this shed infusions were prepared and introduced into new 

 chambers of burnished tin, which had never been permitted to enter our 

 laboratory. After their introduction the liquids were boiled for five 

 minutes in an oil-bath. 



The first experiment in this shed resulted in complete failure. Not 

 one of the infusions exposed to the moteless air of the shed escaped 

 putrefaction. 



Either of two causes, or both of them combined, might, from my 

 point of view, have produced this result. First, a flue from the labora- 

 tory was in free communication with the atmosphere not far from the 

 shed ; secondly, and this was the real cause of the infection, my assistants 

 in preparing the infusions had freely passed between the laboratory to 

 the shed. They had thus incautiously carried the contagium by a mode of 

 transfer known to every physician. 



The infected shed was disinfected ; the infusions were again pre- 

 pared, and care was taken, by the use of proper clothes, to avoid the 

 former causes of contamination. The result was similar to that obtained 

 at Kew, viz. organic liquids which in the laboratory withstood two 

 hundred minutes' boiling, were rendered permanently barren by five 

 minutes' boiling in the shed. 



A third clear issue is thus placed before us, which I should hardly think 

 of formulating before the Royal Society, were it not for the incredible 

 confusion which apparently besets this subject in the public mind. A rod 

 thirty feet in length would stretch from the infusions in the shed to the 

 same infusions in the laboratory. At one end of this rod the infusions 

 were sterilized by five minutes' boiling, at the other end they withstood 

 two hundred minutes' boiling. As before, the choice rests between two 

 inferences : — Either we infer that at one end of the rod animal and vege- 

 table infusions possess a generative power which at the other end they 

 do not possess, or we are driven to the conclusion that at the one end of 

 the rod we have infected and at the other end disinfected air. 



The second inference is that which will be accepted by the scientific 

 mind. To what, then, is the inferred difference at the two ends of the 

 rod to be ascribed '? In one obvious particular the laboratory this year 

 differed from that in which my first experiments were made. On its 

 floor were various bundles of old and desiccated hay, from which, 

 when stirred, clouds of fine dust ascended into the atmosphere. This 

 dust proved to be both fruitful and, in the highest degree, resistant. Prior 



