HISTORICAL 



II 



ing or boiling them and excluding the air by means of a layer of oil or by 

 closing the container with cotton and supplying it with air which had been 

 sterilized by passing through sulphuric acid. Braconnot (1831) advanced 

 the theory that yeast cells had the power of holding, and condensing within 

 the cell-substance, the oxygen of the air and conducting it to the substances 

 undergoing fermentation, resulting in the splitting up of sugar into alcohoi 

 and carbonic acid gas. 



The question of spontaneous generation was again discussed with re- 

 newed energy. The belief that larger animals could originate de novo was 

 quite generally abandoned, but it was very persistently argued that micro- 

 organisms, maggots and a few other very small animals could thus develop. 

 Bastian was perhaps the leader in the arguments in favor of spontaneous 

 generation, opposed by Schwann, Pasteur, and others. Schroeder and von 

 Dusch demonstrated that decay could be prevented by boiling and sup- 





FIG. 3. Flask, containing an organic substance, a, hermetically closed by means of 

 a stopper, b. The bent tube is open at e, admitting air. Dust and microbes lodge at 

 the bends d and c. 



plying air that had been filtered through cotton. Pasteur (1862) used 

 bent tubes to supply air to the previously sterilized (by heating) substance, 

 as shown in Fig. 3. The microbes in the air passing through the tube are 

 deposited (by gravity) in the lower bends of the tube. Those favoring the 

 theory of spontaneous generation nevertheless continued their arguments. 

 It was pointed out that changes of decay took place in eggs, in internal 

 tissues and organs of the dead as well as in the living, etc., where, it was 

 supposed, microbes could not possibly have access. However, further 

 convincing experiments gradually silenced all opposition. Bastian and 

 a few followers took practically their last stand in 1875, and since that time 

 no scientist of repute has ever argued in favor of spontaneous generation, 

 though the question of the primal origin of living things remains un- 

 answered. 



