1911.] On Variation and Adaptation in Bacteria. 549° 
réadily in anaérobic cultures, when it entirely fails to appear under aérobic 
conditions of cultivation. | 
M, V, and H in Mannite. 
H became a mannite fermenter on the third passage, and so remained. 
M and V were carried on in mannite from June 14 until August 1 without 
any change in the reaction appearing. 
These three sets of observations show that by continued passage through 
a particular medium some of the streptococci easily acquire the faculty of 
fermenting a special carbohydrate, to which they had always previously | 
given a negative reaction. In other cases similar changes could not be 
obtained within the period of investigation. 
Inulin Test. 
In the next set of experiments inulin was selected as the medium for 
observation, as being apparently the most difficult for streptococci to ferment. 
Andrewes and Horder found that only 3 per cent. of their streptococci could 
ferment this polysaccharide. 
Five streptococci, L, P, 8, G, M, were selected for observation, none of 
which fermented inulin, and only one of which (G) had ever done so within 
my experience. Table IV shows the result of growing these organisms for 
certain periods in inulin medium. All became eventually (eight weeks) 
strong inulin fermenters. They were then put back into stab agar for three 
months, after which all but M were found to have lost their action upon 
Table LV.—Streptococci L, P, 8, G and M. Showing the Reactions in 
Inulin Medium at Different Stages of the Experiment. 
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