Report on the Bacteriology of Water. 



457 



on the other hand, yielded the typical colonies of the B. coli com- 

 munis, and these were further confirmed by growth in potatoes, and 

 by positive results with the indol and gas-bubble tests. 



The above phenol broth-culture tests were all made with 0*5 and 

 I/O c.c. of the water, but on the same day (5.6.1893) some further 

 experiments were made to incidentally determine whether much 

 smaller volumes (a single drop) of water would react, and, if so, 

 whether with equal rapidity. Thus 



Examination by Phenol Broth-culture of Small Quantities 

 of Infected Water, 5.6.1893. 



The interest attaching to the phenol broth examinations consists in 

 the circumstance that the actual number of typhoid and coli bacilli 

 present in the volumes of water used can be calculated from the 

 results of the plate cultivations made on the same day (see pp. 452 and 

 454). Thus, it will be seen from the tables on pp. 456 and 457, that 

 there was, in nearly all cases, practically no difference in the time 

 which elapsed before the phenol broth tubes became turbid, irrespec- 

 tively of whether 0'5 c.c., 1 c.c., or only 1 drop of the same water was 

 employed ; for, even in the 1 drop of the water, it is apparent from 

 the plate cultivations (p. 452) that there must have been upwards of 



K.OOO typhoid bacilli present, and a still larger number of coli bacilli 

 n those waters infected with this bacillus. 



