VITALITY OF PUTREFACTIVE ORGANISMS. 177 



more conclusive than it would have been had all three 

 tubes remained intact ; for had the power of developing 

 the organisms which produced the turbidity been in- 

 herent in the infusions, its action would not have been 

 confined to a single tube. 



It will be understood that when the chamber is 

 lifted from the oil-bath in which its infusions are boiled, 

 the air within the chamber contracts, and an indraught 

 is the consequence. If the entering air be properly- 

 sifted, by passing it through cotton-wool plugs, no harm 

 is done ; but if it enter an aperture unsifted, it carries 

 its motes along with it. In the beef-chamber just re- 

 ferred to an aperture of this kind, about the size of a 

 pin-hole, was detected. This obviously was the door 

 through which the contagium entered. Through a 

 similar but graver defect in its chamber the sole- 

 infusion also broke down ; but in a subsequent experi- 

 ment with sole-infusion in the Jodrell laboratory, two- 

 thirds of the whole number of tubes charged with it 

 remained free from all trace of life. 



§ 15. Experiments on the Roof of the 

 Royal Institution, 



With a view to making, nearer home, experiments 

 similar to those made at Kew, I had a wooden shed 

 erected on the roof of our laboratory. The shed was 

 provided with benches, water and gas-pipes, and a stove 

 for heating. To an infusion of cucumber, which I had 

 found extremely intractable in the laboratory, my atten- 

 tion was first directed. Two tin chambers of three 

 tubes each were prepared, and transferred to the shed 

 from the workshop where they were made, without 



