XI, B, 4 Wade: Carbohydrate Fermentation 179 



Table VII show the maximal point under these conditions to be 

 between 3.5 and 4.1. 



Beyond the point of sugar concentration required under the 

 conditions obtaining to bring the total acid produced up to the 

 point of tolerance, addition of more sugar does not increase 

 the final acidity. In several instances (see Table IV) 0.5 

 per cent of reagent has proved insufficient to secure maximum 

 fermentation. Further, in a number of instances (as in Table 

 II) reversion to neutral from incomplete acidification of 0.5 

 per cent agar slants occurred. 



Comparative cultivations show that room temperature, which 

 was used by Schobl in his tests, influences fermentation to 

 considerably greater activity than does body temperature. 

 Anaerobic cultivation at the latter heat accelerates, at least 

 temporarily, acid formation sometimes even more than does 

 aerobic cultivation at room temperature. 



The morphology of the organism varies more or less with the 

 sugars, depending not only upon the involuting and degenerating 

 influence of the acid sometimes formed, but also upon other less 

 evident influences where acid is not produced. The extent of 

 growth is also considerably modified, apparently anomalously 

 in different media. In bouillons containing fermentable sub- 

 stances the growth is most luxuriant; on agars containing the 

 same reagents the growths are much less heavy than on unacidi- 

 fied media. In bouillon, because of its fluidity, acid when formed 

 cannot inhibit growth until such time as the entire mass of the 

 medium is brought to the maximum point of acid tolerance. In 

 agar, on the other hand, as soon as the medium directly beneath 

 the growth becomes sufficiently acidified, multiplication seems 

 almost to cease. Further production of acid constantly replaces 

 that lost by diffusion to the deeper levels, and the growth remains 

 light. Thus under different physical conditions the same car- 

 bohydrate produces opposite effects. Occasionally, when acid 

 production in the agar culture is weak, reversion occurs and the 

 primary, light, acid-producing growth is replaced by a heavy, 

 nonfermenting growth. 



Of the three methods of determining acid production, titration 

 of sugar bouillons is by far the best, as is shown particularly 

 by the contrast between the negative or weak and irregular 

 fermentation of salicin, arabinose, galactose, and maltose in 

 the other media and their regular fermentation in bouillons. 

 Only in bouillons did the 0.5 per cent series approximate the 

 1 per cent series in regularity or intensity of reaction. In sugar 



