SPONTANEOUS GENERATION 



II 



arranged that air could be drawn through the flask. The air, 

 however, was first drawn through sulphuric acid, and it was 

 found that when this was done spontaneous generation did 

 not occur in previously boiled decoctions (Fig. 2) . The critics, 



FIG. 2. Schulze's Experiment. Bulbs contain sulphuric acid through which air 

 was drawn before it was allowed to enter the bottle. After Lafar. 



however, said that the sulphuric acid in some way had changed 

 the air. Theodore Schwann, the next year, performed experi- 

 ments similar to those of Schulze, except that he substituted 

 for the sulphuric acid, metal tubes, which were heated red 

 hot when the air was drawn through (Fig. 3). Perhaps 

 Schwann's most important observation was the fact that 

 when certain chemical substances potassium arseniate, 

 etc. were added to these solutions putrefaction did not 

 take place. Schwann may therefore be regarded as the 

 founder of the science of antiseptics. One of the most im- 

 portant experiments supporting the theory of biogenesis was 



