VIII, B, 2 Butler: Carbohydrate Reactions 125 



not the reaction of the media has had to be previously arranged. 

 Some carbohydrates suffer inversion to a lower order if subjected 

 to heat in the presence of weak acid or alkali, and in the finished 

 product we will then find for instance that a supposed Shiga 

 strain of the dysentery bacillus is producing acid in the maltose 

 medium. As a matter of fact, it is simply showing its capacity 

 to ferment glucose inverted from maltose. The question of 

 the indicator is also to be considered. The one generally used 

 is litmus, and this, if subjected to long heating in the presence 

 of organic substances, bleaches out and we are left with a 

 desensitized litmus. The use of litmus, too, as a part of the 

 medium rather than as a pure indicator is a matter to criticize. 

 What chemist would expect his indicator to show a fine shade 

 of reaction if he incorporated that indicator into a mass of 

 organic material, sterilized it on three successive days at 100° 

 C, and then stored it in the ice box for perhaps a month? I 

 have found on a number of occasions that the results varied, 

 particularly when dealing with maltose, if the organism be al- 

 lowed to grow for about three days in the peptone sugar solution, 

 and the indicator be then run in and the results read immediately, 

 from the results obtained by growing the same organism in the 

 same solution, but with the litmus added from the start. If, 

 however, the tubes, to which the indicator was added at the 

 end of the incubation, are set aside for a few hours, they will 

 nearly always show the same results as those to which the litmus 

 was added in the first instance. These statements are not of 

 much importance from the standpoint of indicating variability 

 in the carbohydrate reactions of dysentery bacilli, because with 

 the thousands of trials to which these organisms have been 

 subjected by different observers I believe we are in possession 

 of the exact facts as to what the different strains will do. But 

 they do indicate, it seems to me, that for the individual bacte- 

 riologist, identifying strains of dysentery bacilli from the stools, 

 the media and the methods employed should be revised and sub- 

 jected to standardization. On account of our lack of standards, 

 combined with the inherent tendency of some of our differ- 

 entiating carbohydrates to change during manipulation, I believe 

 we are overlooking at least one perfectly valid variety of Bacillus 

 dysenterise ; namely. Bacillus Y. 



It is manifest that the simpler the solution into which any 

 given carbohydrate is introduced, always provided that the bac- 

 terium will grow luxuriantly in it, the more nearly the facts will 

 be revealed. If we could get organisms to grow in a simple 



