VITALITY OF PUTBEFACTIVE ORGANISMS. 211 



•which the concentrated luminous beam places in our 

 hands, what is the approximate time required for the 

 Bacterial germ to pass into the Bacterium. Say that 

 it is twenty-four hours. Supposing the heat of boiling 

 water, or even a lower heat than that of boiling water, 

 to be applied to the germ immediately before its final 

 development, when all its parts are plastic, when it is, 

 in short, on the point of reaching a stage at which a 

 temperature of 140° Fahr. is demonstrably fatal. It 

 is in the highest degree probable that a temperature of 

 212°, or of 200°, or, indeed, a temperature of 150°, if 

 applied sufficiently often or for a sufficient length of 

 time, will prove fatal to the germ, and prevent the 

 appearance of the still more sensitive organism to 

 which the germ is on the point of giving birth. 



Here, at all events, we have a theoretic finger-post 

 pointing out a course which experiment may profitably 

 pursue. It is not to be expected that the germs with 

 which our infusions are charged aU reach their final 

 development at the same moment. Some are drier 

 and harder than others, and some, therefore, will be 

 rendered plastic and sensitive to heat before others. 

 Hence the following procedure. 



Four-and-twenty small retorts were charged with 

 hay-infusions on the 1st of February, and subjected 

 morning and evening to the boiling temperature for 

 one minute. The last heating took place on the even- 

 ing of the 3rd of February. The retort-necks had been 

 plugged with cotton-wool ; the air within them, how- 

 ever, had not been filtered, and there was comparatively 

 little care bestowed on their preparation. After the 

 final heating they were abandoned to the temperature 

 of a room kept close to 90° Fahr. A series of similar 

 retorts charged at the same time with the same infu- 

 sions were boiled continuously for ten minutes, plugged 



