ISOLATION OF SPECIFIC PATHOGENES 81 



found that certain strains of B. typhi were inhibited, 

 while strains of B. coli developed feebly in the presence 

 of 0.5 per cent of caffein. 



In this country marked success in the isolation of 

 the typhoid bacillus has been attained by the use of 

 lactose bile as an enrichment medium. Jackson (Jack- 

 son and Melia, 1909), the principal exponent of this 

 procedure, recommends that sterilized undiluted fresh 

 ox gall (or an ii per cent solution of dry fresh ox gall) 

 containing i per cent of peptone and i per cent of 

 lactose be made up in 40 c.c. amounts in fermen- 

 tation tubes to which varying amounts of water, up 

 to 10 c.c. may be added. After incubation for 48 

 or 72 hours, he plates on Hesse a gar and he finds 

 that in the bile medium B. typhi tends to over- 

 grow B. coli while most other organisms are entirely 

 suppressed. 



Concentration by Agglutination or Precipitation. A 

 physical concentration of the typhoid bacilli precedes 

 enrichment or isolation in the procedure recommended 

 by many authors. Klein, as noted above, accomplished 

 this by passing the water through a Berkefeld filter. 

 Other workers have made use of agglutination or chem- 

 ical precipitation for the same purpose. 



The phenomenon of agglutination was made the 

 basis of a method of isolating B. typhi from water by 

 Adami and Chopin (Adami and Chopin, 1904). Two- 

 liter samples of the water were collected in sterilized 

 bottles (Winchester quarts), and to each was added 

 20 c.c. of i per cent glucose broth. The sample was 

 incubated for 18 to 24 hours at 37 C., after which 



