BACILLUS DYSENTERIC 377 



growth develops ; on gelatin a white growth nearly limited 

 to the inoculation track, and without liquefaction. The 

 colonies on a gelatin plate closely resemble those of the 

 typhoid bacillus. On potato the growth is either thin, 

 grey and slightly visible, or thicker and yellowish or 

 brownish. The colour of neutral red media is unaltered. 

 Litmus milk first becomes faintly acid, then markedly 

 alkaline ; no clotting. Indole is generally not formed 

 (never by the Shiga type) ; occasionally a trace may be 

 detected. All strains ferment glucose with the formation 

 of acid only, no gas ; none ferment lactose. Some strains 

 (the Flexner type) ferment mannitol with the formation 

 of acid only, no gas ; other strains (the Shiga-Kruse type) 

 have no action on this alcohol. The principal fermenta- 

 tion and other reactions are given in the Table on p. 381. 

 These reactions are very variable with different stains, 

 but differentiation may be accomplished by agglutination, 

 saturation, and complement fixation, tests. Shiga x dis- 

 tinguishes five groups of dysentery bacilli as follows : 



1. Fermenting dextrose alone [Shiga, Kruse, Flexner 



(Newhaven)]. 



2. Fermenting dextrose and mannitol (Hiss and Russell's 



Y bacillus, Ferran, Seal Harbour bacillus). 



3. Fermenting dextrose, mannitol and saccharose 



[Flexner, Strong (Manila)]. 



4. Fermenting dextrose, mannitol, maltose and saccha- 



rose (Harris, Gay, Woolstein). 



5. Fermenting dextrose and maltose, and giving a feeble 



acid reaction with mannitol (Shiga). 



Bahr found occasional variations in fermentive power 

 after sub-culturing and after a sojourn in flies. 



Agglutination reaction. The agglutination reaction is 

 given by the blood of patients suffering from the bacillary 



1 Zeitsch. f. Hyg., Ix, 1908, pp. 75, 120. 



