226 BACTERIOLOGICAL EXAMINATION OF WATER. 



water supplies during epidemics of enteric fever. The cause of 

 this failure has been variously interpreted. Some bacteriologists 

 believe it is due to the feeble vitality of the B. typhosus when 

 associated with other micro-oganisms, especially the B. coli, so 

 that the specific organism dies out of the water supply before 

 the outbreak of disease has directed attention to the necessity of 

 a bacteriological examination of the water. Other bacteriologists 

 would, however, attribute the failure to the imperfection of modern 

 bacteriological methods of investigation. A French school , headed 

 by Rodet and Roux, believes in the existence of transitional forms 

 between the typical B. typhosus and the typical B. coli. Rodet has 

 quite lately described such transitional forms which are of great 

 interest to students of epidemiology. In May 1897, Rodet isolated 

 from the spleen of a fatal case of enteric fever a bacillus which 

 resembled the typhoid bacillus in its morphology, mode of growth 

 on gelatine and agar, absence of gas production in sugar media, and 

 failure to produce indol in peptone solution. Immediately after 

 isolation it was not agglutinated by anti-typhoid serum, even 

 in a dilution of 1-10, and produced a brownish-yellow growth on 

 potato ; consequently the organism appeared to be an atypical 

 coli. The microbe was preserved for a year and its power of 

 reacting to anti-typhoid serum tested from time to time. It 

 was found that the reaction to specific agglutinins gradually 

 increased until, finally, the bacillus was agglutinated by a specific 

 serum diluted 1-100,000. In October 1897, a similar bacillus, 

 which showed a steady increase in its reaction to anti-typhoid 

 serum, was also isolated from the spleen of a fatal case of typhoid 

 fever. A third bacillus, which more strongly resembled B. coli 

 and produced gas in glucose-agar, was recovered from the spleen 

 of a fatal case of enteric fever in December 1897. Six months 

 after its isolation this microbe, which at first was not affected 

 by anti-typhoid serum, was found to be agglutinated by two 

 different sera in exactly the same manner as a typical B. typhosus. 

 On the other hand, Remlinger and Schneider state that they 

 have isolated the B. typhosus from the stools of patients w r ho 

 were not suffering from enteric fever. Four of the bacilli 

 isolated were pathogenic to guinea-pigs, and preventive injections 

 of anti-typhoid serum preserved animals from infection. Inde- 

 pendently of the above bacteria the same observers stated that 



