106 ELEMENTS OF WATER BACTERIOLOGY. 



The English bacteriologists have ascribed much impor- 

 tance as indicators of sewage pollution to another group 

 of organisms, the anaerobic spore-forming bacilli, of which 

 the B. sporogenes is a type. This form was isolated by 

 Klein (Klein, 1898; Klein, 1899) in 1895, in the course 

 of an epidemic of diarrhoea at St. Bartholomew's Hos- 

 pital, and described under the name of B. enteritidis 

 sporogenes; it is apparently identical with the B. aero- 

 genes capsulatus of Welch (Welch and Nuttall, 1892). 



Klein's procedure for isolating the B. sporogenes is 

 simple in the case of polluted waters. A portion of the 

 sample to be examined is added to a tube of sterile milk, 

 which is then heated to 8o° C. for ten minutes to destroy 

 vegetative cells. The milk is then cooled and incubated 

 under anaerobic conditions, which may be accomplished 

 most conveniently by Wright's method. A tight plug of 

 cotton is forced a quarter way down the test-tube, the 

 space above is loosely filled with pyrogallic acid, a few 

 drops of a strong solution of caustic potash are added, 

 and the tube is tightly closed with a rubber stopper. After 

 eighteen to thirty-six hours at 37 the appearance of the 

 tube will be very characteristic if the B. sporogenes is 

 present. "The cream is torn or altogether dissociated 

 by the development of gas, so that the surface of the 

 medium is covered with stringy, pinkish-white masses of 

 coagulated casein, enclosing a number of gas-bubbles. 

 The main portion of the tube formerly occupied by the 

 milk now contains a colorless, thin, watery whey, with a 

 few casein lumps adhering here and there to the sides of 



