NOTES AND MEMOKANDA. 
47 
Professor Tyndall’s Researches on Bacteria, — Dr. Tyndall re- 
cently presented an important paper to the Royal Society on the 
difficulty of destroying Bacteria in solutions. The memoir, although 
appearing only in abstract, is too long for insertion here. However, 
the following portion is of especial interest. After dealing with 
various processes of destroying germs in solution, he says : — “Another 
mode of sterilization, equally certain and perhaps still more remark- 
able, was forced upon me, so to speak, in the following way : In a 
multitude 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 fre- 
quently 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. Above the 
scum, moreover, the interior surfaces of the bulbs used in my experi- 
ments 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 fermenta- 
tion depends on the continuance of life without air — other organisms 
than Torula being also shown competent to live without oxygen. 
Experiment 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 be completely removed from the infusions, there is 
every reason to believe that sterilization without boiling would in most, 
if not in all cases, be the result. But, passing from probabilities to 
certainties, it is a proved fact, that in numerous cases unboiled infu- 
sions deprived of air by five or six hours’ action of the Sprengel pump 
are reduced to permanent barrenness. In a great number of cases, 
moreover, where the unboiled infusion would have become cloudy, 
exposure to the boiling temperature for a single minute sufficed 
completely to destroy the life already on the point of being extin- 
guished through defect of air. With a single exception, I am not sure 
that any infusion escaped sterilization by five minutes’ boiling after 
it had been deprived of air by the Sprengel pump. These five minutes 
accomplished what five hours often failed to accomplish in the pre- 
sence of air. 
VOL. XVIII. 
E 
