SPONTANEOUS GENERATION 



21 



and_Dusch in 1859 (Fig. 4). It remained for Chevreuil and 

 Pasteur to overcome this objection in 1861 by the use of 



Fig. 3. — Schwann's experiment. After boiling, as shown in the diagram, 

 and cooling, air was drawn into the flask by aspiration while the coiled tube 

 was kept hot with the flame. 



i»HlTllimillllllHIIHHiiiii>:n|ir.f^fHiiiiill 



Fig. 4. — Schroeder and Dusch's experiment. The aspirating bottle drew 

 the air through the flask after it had been filtered by the cotton in the 

 tijbe 



