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." 1 



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 tubulure (Fig. 14) 



1 fitudes sur la biere, p. 118. 



