236 



Prof. J. Tyndall on the Deportment of 



[May 17, 



If properly followed out, the method of sterilization here described is 

 infallible. A temperature, moreover, far below the boiling-point suffices 

 for sterilization *. 



Another mode of sterilization, equally certain and remarkable, was 

 forced upon me, so to speak, in the following way. In a multi- 

 tude of cases a thick and folded layer of fatty scum, made up of 

 matted Bacteria, gathered upon the surfaces of the infusions, the 

 liquid underneath becoming sometimes cloudy throughout, but frequently 

 maintaining a transparency equal to that of distilled water. The living 

 scum-layer, as Pasteur has shown in other cases, appeared to possess the 

 power of completely intercepting the atmospheric oxygen, appropriating 

 the gas and depriving the germs in the liquid underneath of an element 

 necessary to their development. 



Placing the infusions in flasks, with large air-spaces above the liquids, 

 corking the flasks, and exposing them for a few days to a tempera- 

 ture of 80° or 90° F., at the end of this time the oxygen of the 

 superjacent air seems completely consumed. A lighted taper plunged 

 into the flask is immediately extinguished. Above the scum, moreover, 

 the interior surfaces of the bulbs used in my experiments were commonly 

 moistened by the water of condensation. Into it the Bacteria sometimes 

 rose, forming a kind of gauzy film to a height of an inch or more above 

 the liquid. In fact, wherever air was to be found, the Bacteria followed it. 

 It seemed a necessity of their existence. Hence the question, What will 

 occur when the infusions are deprived of air ? 



I was by no means entitled to rest satisfied with an inference as an 

 answer to this question; for Pasteur, in his masterly researches, has 

 abundantly demonstrated that the process of alcoholic fermentation 

 depends on the continuance of life without air — other organisms than 

 Torula being also alleged to be competent to live without oxygen. Experi- 

 ment alone could determine the effect of exhaustion upon the particular 

 organisms here under review. 



Air-pump vacua were first employed, and with a considerable measure 

 of success. Life was demonstrably enfeebled in such vacua. 



Sprengel pumps were afterwards used to remove more effectually both 

 the air dissolved in the infusions and that diffused in the spaces above 

 them. The periods of exhaustion varied from one to eight hours, and 

 the results of the experiments may be thus summed up : — Could the air 



* On reading my paper, previous to its presentation to the Koyal Society, Mr. 

 Huxley suggested a continuous exposure to a temperature not much above the death- 

 temperature of the adult Bacterium. I had also noted the experiment for execution 

 myself. It was made some weeks ago with perfect success. The most obstinate infu- 

 sions, maintained for a few days at a temperature of 160° F., are sterilized.— 

 [June 21.] 



