BY R. GREIG SMITH. 741 



typhi itself. On this account the most that can be done is to 

 eliminate as far as possible the harmless bacteria and investigate 

 the others. Many processes have been recommended for this 

 purpose, and of these some have been shown to be worthless, 

 whilst others are apparently of some value. The methods depend 

 upon the inability of the water bacteria to grow upon special 

 media or ordinary media with the addition of (1) phenol, (2) 

 acids, (3) alkalies, or (4) salts. 



The addition of phenol or carbolic acid to ordinary media or to 

 special media has been most frequently advised, and in enum- 

 erating the various methods a beginning may be made with it. 

 Dunbar has shown that the growth of the typhoid bacterium is 

 interfered with by the presence of 0*116% of phenol in water or 

 nutrient media, while 0144 checks the growth entirely. In 

 publishing these facts he showed the uselessness of some methods 

 in which percentages of phenol greater than 0-116 were employed 

 for the separation of Boot, typhi. A method devised by Vincent 

 is not open to Dunbar's objection. 



Vincent's method. — Five drops of a 5% solution of phenol are 

 added to tubes containing 10 c.c. of nutrient bouillon, and into 

 these small increasing quantities of the water under examination 

 are introduced. The tubes are incubated at 42° C, and any 

 that show a growth are used for the preparation of plates of solid 

 media. The colonies that grow in the plates are examined and 

 the bacteria determined by the appearances and reactions of sub- 

 cultures. Bandi* also advises the employment of phenol, but at 

 a comparatively high temperature. 



BaniWs method. — 200 c.c. of bouillon are added to 2 litres of 

 water and the mixture is incubated for 5 hours at 45° C. Twelve 

 drops of the mixture are then added to 10 c.c. of peptone-free 

 bouillon, together with 5 drops of 5% phenol. From the culture 

 twelve successive transfers are made into the carbolised medium, 

 the cultures being maintained at 45° C. The twelfth subculture 



♦Bandi, Centralblatt ftir Bakt. 1 Abt. xxiv., 585, Kef. 



