PUTEEFACTION AND INFECTION. 109 



The tubes were exposed on the 4th of December, all 

 of them being then clear. In the orchid-house the 

 turnip became cloudy on the 7th, the beef and mutton 

 on the 8th, after which the opacity rapidly increased. 

 In the study all remained clear until the 9th, when the 

 turnip began to cloud. On the 1 1th the beef was still 

 clear, while the mutton had given way. On the 1 3th 

 all of them had yielded. In the conservatory the turnip 

 began to cloud on the 10th; the others followed in 

 the same order as in the other cases. 



The influence of temperature seems well shown 

 by these observations. Three days suflBced to cloud the 

 turnip in the orchid-house, five days in the study, and 

 six days in the conservatory. The mutton in the study 

 gathered over it a thick blanket of Penwillium. On 

 the 1 3th it had assumed a light brown colour, ' as if by 

 a faint admixture of clay;' but the infusion became 

 transparent. • The 'clay' here was the slime of dormant 

 or dead Bacteria, the cause of their quiescence being 

 the blanket of Penicillium. I found no active life in 

 this tube, while all the others swarmed with Bacteria. 

 From the Crystal Palace at Sydenham Mr. Price sent 

 me tubes of mutton, beef, and turnip charged with 

 Bacteria. The temperature was low at night, the 

 development of life being thereby considerably retarded. 



Thus, wherever it has been tested, the atmosphere 

 has been found charged with the germs of Bacteria. 



I wished, however, to obtain clearer and more defi- 

 nite insight as to the diffusion of atmospheric germs. 

 Supposing a large shallow tray to be filled with a suitable 

 organic infusion and exposed to the air. Into it the 

 germs would drop; and could the resulting organisms 

 be confined to the locality where the germs fell, we 

 should have the floating life of the atmosphere mapped^ 



