68 Royal Society;-— Prof, J. Tyndall on tie 



lion: while twelve similar lubes, prepared at the same time, in 

 precisely the same way, and exposed to the ordinary air, are 

 clogged with mycelium, mould, and Bacteria.^ 



With regard io the calcined air, a similar propagating-glass was 

 caused to cover twelve other tubes filled with the same infusions. 

 The " glass'' was exhausted and carefully filled with air which had 

 passed through a red-hot platinum tube containing a roll of red- 

 hot platinum gauze. Tested by the searching beam, the calcined 

 air Mas found quite free from floating matter. Not a speck has 

 invaded the limpidity of the infusions exposed to it, while twelve 

 similar tubes placed outside have fallen into rottenness. 



The experiments with calcined air took another form. Six years 

 ago it was found that, to render the laboratory air free from float- 

 ing matter, it was only necessary to permit a platinum wire heated 

 to whiteness to act upon it for a sufficient time. Shades containing 

 pear-juice, damson-juice, infusions of hay and turnip, and water 

 of yeast were freed from their floating matter in this way. The 

 infusions were subsequently boiled and permitted to remain in 

 contact with the calcined air. They are quite clear to the present 

 hour, while the same infusions exposed to common air became 

 mouldy and rotten long ago. 



It has been affirmed by other writers on this question that tur- 

 nip- and hay-infusions rendered slightly alkaline are particularly 

 prone to exhibit the phenomena of spontaneous generation. This 

 was not found to be the case in the present investigation. Many 

 such infusions have been prepared, and they have continued for 

 months without sensible alteration. 



Finally, with regard to infusions wholly withdrawn from air, a 

 group of test-tubes containing different infusions was boiled under 

 a bell-jar first filled with filtered air, and from which the air was sub- 

 sequently removed as far as possible by a good air-pump. They 

 are now as pellucid as they were at the time of their preparation 

 more than two months ago, while a group of corresponding tubes 

 exposed to the laboratory air have all fallen into rottenness. 



There is still another form of experiment on which great weight 

 has been laid — that of hermetically sealed tubes. On the 6th of last 

 April a discussion on the " Grerm-Theory of Disease " was opened 

 before the Pathological Society of London. The meeting was attended 

 by many distinguished medical men, some of whom were profoundly 

 influenced by the arguments, and none of whom disputed the facts 

 brought forward against the theory on that occasion. The following 

 important summary of these was then given by Dr. Bastian: — . 

 ""With the view of settling these questions, therefore, we may care- 

 fully prepare an infusion from some animal tissue, be it muscle, 

 kidney, or liver ; we may place it in a flask whose neck is drawn 

 out and narrowed in the blowpipe-flame, we may boil the fluid, 

 seal the vessel during ebullition, and, keeping it in a warm place, 

 may await the result, as I have often done. After a variable time, 

 the previously heated fluid within the hermetically sealed flask 

 swarms more or less plentifully with Bacteria and allied organisms." 



