TYPHOID COLON GROUPS. 85 



tin- age and size of the individual treated. Susceptibility is reduced 

 about one-fourth, and of those attacked after previous vaccination, the 

 mortality is only about one-fourth of what it is among the noninocu- 

 lated. 'Strong prepares a prophylactic vaccine from living plague 

 cultures rendered avirulent. Yersin's serum, made by injecting horses 

 with dead plague cultures and afterward with living ones, is of value 

 prophylactically and has possibly considerable curative power. 



The Eberth, Gartner and Escherich Groups. From a stand- 

 point of cultures in litmus milk and sugar bouillon we can divide the 

 organisms related to typhoid at one extreme and the colon at the other 

 into three groups. 



1. The Eberth or typhoid group. There are three important 

 pathogens in this group: the B. typhosus, the B. dysenteriae, and the 

 B. fecalis alkaligenes. The color of litmus milk is practically unal- 

 tered, and there is no gas production in either glucose or lactose bouillon. 

 No coagulation of milk. No reduction of neutral red. The B. 

 typhosus and the B. fecalis alkaligenes are actively motile, while the B. 

 dysenteriae is nonmotile or practically so. 



During the first 24 to 48 hours there is a moderate acid production 

 by typhoid, so that the milk culture is less blue, while with the B. 

 fecalis alkaligenes the alkalinity is intensified from the start so that 

 the blue color is deepened. 



2. The Gartner or hog cholera group. Besides organisms im- 

 portant for animals and probably at times for man, such as B. cholerae 

 suum and B. psittacosis and B. icteroides (interesting historically as 

 having been reported as the cause of yellow fever by Sanarelli), we have 

 two pathogens: (i) B. enteritidis (Gartner's bacillus) and (2) B. 

 paratyphoid B. These organisms cannot be separated culturally, but 

 only by immunity reactions. They do not tarn litmus milk pink. 

 They produce gas in glucose bouillon, but not in lactose. They very 

 powerfully reduce neutral red with the production of a yellowish 

 fluorescence. They do not coagulate milk. There is a transient 

 acidity in the litmus milk, but becoming shortly afterward alkaline, 

 the lilac-blue color is intensified. Both organisms are motile. 



3. The Escherich or colon group. These turn litmus milk pink, 

 coagulate milk, reduce neutral red and show varying degrees of 



