422 BACTERIOLOGY. 



with blood from other febrile conditions. It is said by 

 Johnston and McTaggart^ that they can be prevented 

 if cultures of just the proper degree of vitality are em- 

 ployed ; and this corresponds with the results of a fairly 

 wide personal experience with the test. 



The blood of certain animals, as well as a number of 

 chemical substances, such as corrosive sublimate, alco- 

 hol, salicylic acid, resorcin, and safranin in high dilution, 

 cause agglutination of the typhoid bacilli ; but the reac- 

 tion is not specific, for in most cases they have the same 

 effect on other motile bacilli. 



The method is still in the experimental stage, and 

 there are numerous features not entirely clear. In 

 the light of present experience, however, it is fair 

 presumptive evidence that the serum is from a case 

 of typhoid fever when unmistakable agglutination and 

 cessation of motion are seen in from fifteen to twenty 

 minutes after typhoid bacilli are mixed with the serum 

 of a suspicious febrile condition. 



All the preceding points should be borne in mind in 

 the examination of drinking-water supposed to be con- 

 taminated by typhoid dejections, for the organisms 

 which most closely approach the typhoid bacillus in 

 growth and morphology are just those organisms which 

 would appear in water contaminated from cesspools — 

 i. e., the organisms constantly found in the normal intes- 

 tinal tract. Even in the stools of typhoid-fever patients 

 the presence of these normal inhabitants of the intes- 

 tinal tract renders the isolation of the typhoid organisms 

 somewhat troublesome. 



Methods of Isolating the Typhoid Bacillus. 

 ^Bacillus typhosus is so variable in many of its bio- 

 ' Johnston and McTaggart: Montreal Medical Journal, March, 1897, 



