XI, B. 4 Wade: Carbohydrate Fermentation 169 



agars as do the quantities of growth on these media. Here is 

 found with regularity extensive, typical chain formation, often 

 with an almost sheathlike capsular layer. In media containing 

 substances such as glycerin and arabinose, which are not fer- 

 mented and in which growth is not heavy, chain formation is not 

 a feature and loose bacillary forms predominate. Stalactites do 

 not develop in such media. Galactose bouillon, it may be noted, 

 produces typical, short, bipolar forms rather more constantly 

 than any other. Filamentous forms occasionally appear which, 

 particularly when tangled, resemble streptothricial organisms; 

 they do not occur regularly enough to seem characteristic fea- 

 tures of any particular medium. 



INFLUENCE OF SUGAR AND MEDIUM ON AMOUNT OF GROWTH 



The amount of growth in these sugar media varies widely, 

 and the effect of the same sugar differs remarkably, depending 

 on the type of medium. In the bouillons the growth is usually 

 heaviest in those in which acid production is most marked and the 

 lighter growths occur with those sugars not affected. Thus in 

 dextrose bouillon, for instance, the growth is very heavy, with 

 a coarse, fiocculent deposit on the bottom and the sides. On 

 dextrose agar, however, the reverse holds true, the growth here 

 being very quickly inhibited by the acid produced. In the bou- 

 illons dextrose, mannite, and levulose have given the heaviest 

 development; maltose, dextrin, and galactose somewhat less; 

 while only fair amounts of growth occurred in the remaining 

 sugars except amygdalin, sorbite, and glycerin, which seemed 

 distinctly unfavorable. These differences were more marked 

 after three than after ten days. 



With the agar media, growth seems promptly to cease once 

 the underlying medium becomes acidified. If this occurs early, 

 the growth is very light; if later, it is correspondingly heavier. 

 Whenever reversion to neutral occurs, the growth, having been 

 temporarily retarded, goes on to maximum. Due to the operation 

 of this rule the growths of the series I maltose set, in particular, 

 varied widely. 



In none of the serum waters has the growth appeared heavy, 

 though from the nature of the material it is difficult to observe 

 this feature with accuracy. 



ANALYSIS OP FERMENTATION REACTIONS 



Consideration of the inconstant and conflicting reactions ob- 

 tained by the use of certain of these media brings up the question 

 of the several factors concerned in the irregularities. These 



144094 2 



