Report on the Bacteriology of Water. 



189 



cate plates cannot fail to take place if they are preserved until wide- 

 spreading liquefaction of the gelatine has occurred. 



1. Bacteriological Examination of the Thames Water previous to Infec- 

 tion with Anthrax. 



From Table I it will be seen that the unfiltered water contained a 

 large number of micro-organisms, which was, however, much reduced 

 by the simple process of nitration through Swedish paper. The 

 colonies obtained showed the micro-organisms to be of numerous 

 different kinds, many of them being easily recognisable as belonging 

 to the forms which have already been described and figured by me 

 three years ago (Grace C. and Percy F. Frankland, ' Zeitsch. f. 

 Hygiene,' vol. 6, 1889) as occurring in Thames water, and a brief 

 resume of which is given in the following table. Owing to a 

 large number of the colonies causing liquefaction of the gelatine, 

 their numerical estimation is much interfered with, and in order to 

 some extent obviate this difficulty, it will be seen that plates were 

 not only poured with the undiluted waters, but also with the waters 

 after large dilution (50 times their volumes) with sterilised water, 

 so as to obtain a smaller number of colonies on the plate. This expe- 

 dient has always been resorted to in cases where an inconveniently 

 large number of colonies was to be expected ; in all cases, however, 

 the results are calculated to the number of colonies obtained from 

 1 c.c. of the water in the undiluted state. 



Table I also shows that the filtration through porcelain, as well as 

 the steaming, were effectual in sterilising the water, the number of 

 colonies obtained in these cases being no greater than would appear 

 on blank plates. 



The unfiltered Thames water, and that which had been passed 

 through Swedish paper, were again examined on October 26, 1892, 

 or more than seven months after the experiments were commenced ; 

 in both cases the flasks which had been kept in the incubator con- 

 tained more organisms than those which had been in the refrigerator, 

 but in all cases the numbers were comparatively small, and in the 

 unfiltered water had fallen much below what they were at the begin- 

 ning. 



