PROCEDURE FOR EXAMINATION OF WATER. 283 



water to glucose-formate broth tubes, and then incubate in 

 Buchner's tubes at 42 C. (Fakes' method). Plate out all the 

 tubes which show any turbidity after twenty-four hours 

 incubation in gelatine and on alkaline glucose-litmus-agar. 



(d) Examine all the plates for B. coli and other sewage 

 organisms. 



Sub-culture the coliform colonies in : 



Glucose-gelatine shake, for gas formation. 



Milk, for acidity and coagulation of casein. 



Peptone (Witte) water, for the indol reaction. 



Agar-slope, for agglutination test. 



If B. typhosus be suspected, all the tests given under the 

 description of this organism must be applied. 



(2) If the specimen of water contains a very large number 

 of micro-organisms, it is useless to plate out the concentrated 

 sample directly in carbol-gelatine. 



The best plan is to cultivate the concentrated water in amounts 

 varying from 0*1 to 1 c.c. in glucose-formate broth, according 

 to Pakes' method, and in carbolic acid broth containing not 

 more than 1*0 per cent, carbolic acid. The growths which 

 result must be plated out on alkaline glucose-litmus-agar. 



(3) If the water is suspected to contain the cholera spirillum, 

 to 90 c.c. of the sample add 10 c.c. of the stock peptone 

 solution (10 per cent, peptone, 20 per cent, gelatine, and 5 per 

 <,'ent. salt) and cultivate the mixture at 37 C. After twelve 

 hours incubation remove loopfuls from the surface, and examine 

 in a hanging-drop for spirilla ; if these are not in pure culture 

 inoculate a loopful into a second flask, containing 1 per cent, 

 peptone and | per cent. salt. Plate out loopfuls from the 

 surface of the pure culture in gelatine and on agar. Then 

 inoculate peptone tubes for the indol reaction, and stab- 

 gelatined for the typical liquefaction ; also plant out a loopful 

 on an agar-slope, and employ the growth, which results in 

 twenty-four hours, for Pfeitfer's reaction and the agglutination 

 test. 



