BACILLUS DYSENTERIM 441 



The colonies upon agar-agar present nothing charac- 

 teristic ; those on gelatin are at first — i. e., just after iso- 

 lation from the body — like those of bacillus typhosus ; 

 later on, after the organism has been kept under condi- 

 tions of continuous saprophytic growth, the colonies may 

 be thicker, denser, moister, and less translucent, but 

 always suggesting the peculiar, leaf-like contour char- 

 acteristic of the colonies of the colon-typhoid group 

 under similar conditions. In gelatin stab-cultures there 

 is growth along the track made by the needle, and little 

 tendency to lateral development over the surface. 



On potato, its growth may be so limited as to be 

 scarcely visible, or it may appear as a moderately volu- 

 minous grayish-brown or light-brown layer along the 

 track made by the needle, and spreading laterally be- 

 yond this. Between these extremes all gradations may 

 be seen according to the suitability of the potato used. 



In bouillon it causes uniform clouding and a more or 

 less dense sediment. It does not form a pellicle. 



Growth on blood-serum is not accompanied by lique- 

 faction (digestion). 



Glycerin agar-agar appears less suited to its growth 

 than plain nutrient agar-agar. 



It does not ferment either glucose, saccharose, or lac- 

 tose, with liberation of gas ; although in glucose media 

 there is a slight increase of acidity. 



When grown in litmus-milk, the latter after twenty- 

 fonr to seventy-two hours at body-temperature becomes 

 a pale lilac. Later on — i. e., after six to eight days — 

 there is a development of alkali, and the lilac tint gives 

 way to a deep, distinct blue color. Coagulation is never 

 observed. 



It is either incapable of producing indol, or has this 



