6 THE THEORY OF SPONTANEOUS GENERATION. 



tions of the investigator, the contents of the flask when opened 

 being found free from living organisms, which, however, soon 

 made their appearance when the open flask 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. 



v Three years later, THEODOR SCHWANN (II.) entered the field as 

 an opponent of the theory of spontaneous generation. Of his 



labours in this 

 direction, a slight 

 modification of 

 the Schultze ex- 

 periment, consist- 

 ing chiefly in the 

 substitution of a 

 heated metal tube 

 for the bulb tubes 

 (see Fig. 2), occu- 

 pies merely a sec- 

 ondary position. 

 More important 

 in the attack on 

 the theory of the 

 spontaneity of the 

 phenomena of fer- 

 mentation was the 

 establishment by him of the fact that a resort to heat is unnecessary 

 in the prevention of such decomposition, 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, potassium arseniate, &c." 

 He was, therefore, the founder of the science of antiseptics. Con- 

 cerning 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 Sch warm'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 com- 

 position. 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 ordi- 

 nary air could be deprived of its property of inducing crystallisa- 

 tion in a supersaturated solution of sodium sulphate by filtration 



FlO. 2. Theodor Schwann's Experiment. 



