THE LABOrRS OF SCHRODKH AM) DI'SCII 5 



opened being found free from living organisms, wnich, however, .soon nuule then- 

 appearance when the open fl.-i.sk was freely exposed to the air. This proved that 

 previous exposure to the influence of fire is not an essential condition for 

 depriving air of the power of inducing fermentation or putrefaction. 



Three years later, Tincoixm ScmvAXX (II.) rnfeivil f,he fii-ld a,s an opponent 

 of the theory of spontaneous genera,! ion. Of his labours in this direction, a 

 slight modification of tho Schnlt/e experiment, consisting chiefly in the substi- 

 tution of a heated metal tube for the bulb tubes (see Fig. 2), occupies merely a 

 secondary position. More 

 important in the attack on 

 the theory of the spon- 

 taneity of the phenomena 

 of fermentation was the 

 establishment by him of 

 the fact that a resort to 

 heat is unnecessary in the 

 prevention of such decom- 

 position, but that the same 

 result can be attained by 

 the addition of some toxic 

 substance to the liquid : 

 " Fermentation is arrested 

 by any influence proved 

 capable of killing the fungi, 



especially by heat, pOtaS- Fro. 2. Theoclor Schwann's Experiment. 



sium arseniate, &c." He 



was, therefore, the founder of the science of antiseptics. Concerning his 

 fundamental researches in the narrower field of alcoholic fermentation, mention 

 will be made in a subsequent chapter. 



The adherents of spontaneous generation applied to Schwann's method of 

 purifying the air the same objection (referred to above) which they had previously 

 lodged against Spallanzani. They did not even consider themselves confuted by 

 the results of Schultze's experiment, but asserted that here also the treatment of 

 the air, although by no means so violent, unfavourably modified its composition. 

 The refutation of this doubt was only accomplished after a lapse of seventeen 

 years, and that by 



6. The Labours of Schroder and Dusch (I.). 



Instigated by the researches of Loewel, who found that ordinary air could be 

 deprived of its property of inducing crystallisation in a supersaturated solution 

 of sodium sulphate by filtration through cotton-wool, the two investigators 

 named above modified, in 1853, the arrangement of Schultze's experiment, by 

 allowing the incoming air to pass through a glass tube packed with cotton-wool 

 before entering the flask. It was found that by means of this (decidedly not 

 " violent ") treatment the air also lost its power of causing decomposition and 

 the formation of minute organisms in extracts which would remain unchanged 

 when air was excluded. 



The importance of this demonstration must not, however, be over-estimated, 

 for it only proves the presence in the air of a "something '' capable of giving 

 rise to living creatures in inanimate nutrient media, and of exciting substantive 

 changes (fermentation and putrefaction) therein. Concerning the nature of this 

 active ''something," the experimenters could give no satisfactory account; they 

 even left it an open question whether the something was gaseous or not. It 



