746 BACTERIAL FLORA OF THE SYDNEY WATER SUPPLY, 



Neufeld* were able by this method to separate Bact. typhi from a 

 polluted water. Bact. coli was not present, from which they 

 concluded that the pollution had been caused by the access of 

 the urine of typhoid patients. 



Other writers have experimented with the selective action of 

 salts, acids, and alkalies in separating typhi and coli from water. 

 TJffelmannf found that the former could withstand considerable 

 quantities of citric acid, acetic acid or alum. He advised the 

 addition of 10% citric acid and 0-25% methylviolet to ordinary 

 nutrient gelatine. Dunbar, however, objected to his method, 

 as it did not distinguish between coli and typhi. Riedal} pro- 

 posed the use of iodine trichloride. Kohler§ showed the action 

 of various organic and inorganic acids, alum, phenol, the alkaline 

 hydrates and stains upon the growth of typhi. Fermi || has 

 recorded the resistance of various bacteria to increasing doses of 

 certain chemicals. The bacteria are chiefly pathogenic, and 

 although the table can be used for separating the bacteria of 

 certain groups, yet there is no indication of the usefulness in 

 isolating noxious from innocuous water bacteria that might have 

 been expected from a paper which entailed a vast amount of 

 work. There are some points, however, that may be noted, The 

 micrococci (including the pyogenic varieties) may be separated 

 from other bacteria by growth upon agar containing up to 10 

 drops of potassium hydrate in every 5 c.c. of medium. Bact. 

 typhi has little power of resistance towards most chemicals. The 

 varieties of Bact. coli commune and the fluorescent bacteria can 

 withstand up to 10 drops of 5% (presumably by weight), of 

 hydrochloric acid per 5 c.c. agar. Bact. coli commune begins to 

 be affected when 10-16 drops of 5% potassium iodide are added to 

 5 c.c. agar, while Bact. typhi is affected when 5-6 drops are 



* Kiibler und Neufeld, Zeit. fur Hygiene, xxxi., 133. 



t Uffelrnann, Centralblatt fur Bakt. 1 Abt. xi., 218, Ref. 



+ Riedal, see Holz, Centralblatt fur Bakt. 1 Abt. ix., 293, Ref. 



§K6hler, Centralblatt fur Bakt. 1 Abt xiv., 89, Ref. 



|| Fermi, Centralblatt fiir Bakt. 1 Abt. xxiii., 208, 266. 



