1876.] Phenomena of Putrefaction and Infection. 175 



knowledge is not stated. The author is certainly not among the 

 number, though he has sought anxiously for knowledge of the kind. He 

 thus tests the statements in succession. 



And first, with regard to filtered air. A group of twelve large test-tubes 

 was caused to pass air-tight through a slab of wood. The wood was coated 

 with cement, in which, while hot, a heated " propagating-glass " resem- 

 bling a large bell- jar was imbedded. The air within the jar was pumped 

 out several times, air filtered through a plug of cotton- wool being per- 

 mitted to supply its place. The test-tubes contained infusions of hay, 

 turnip, beef, and mutton — three of each, twelve in all. They are as 

 clear and cloudless at the present moment as they were upon the day of 

 their introduction ; while twelve similar tubes, 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 to 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 was found quite free 

 from floating matter. JSTot 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 floating 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 turnip- 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 subsequently 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 

 vol. xxiv, • o 



