TRANSFORMATION OF ONE SPECIES INTO ANOTHER 195 



unfitted for transformation, if this transformation were 

 really possible? 



"It was, then, to avoid this embarrassment, that I 

 resolved to modify entirely the conditions of the ex- 

 periment, and to apply to the research which I had in 

 view a culture method which would suppress completely, 



Fig. 14. 



-Flask used by Pasteur in his study of the transformation of 



species. 



or at least very nearly, the sole cause of error which I 

 had encountered, that is the possible falling of germs or- 

 of yeast cells from the air during the manipulation."'^ 



To carry out this idea, Pasteur added to the flask 

 with the curved neck which he had used in his studies on 

 spontaneous generations, a second tulxilure (Fig. 14) 



1 Etudes sur la biere, p. 118. 



