ii;H BACTERIOLOGICAL EXAMINATION OF WATER. 



gelatine 4 grammes, and a solution of soda sufficient to give a 

 slight alkalinity. The flasks are sterilised in the autoclave, and 

 then 150 c.c. of the suspected water are added to each of them. 

 The flasks and contents are incubated at 37 C. ; if a film appears 

 on the surface after eight to twelve hours, loopfuls are removed 

 and treated as above described. 



Sanarelli employed a similar method. He placed 200 c.c. of 

 the water in a sterilised flask sufficiently large to allow a con- 

 siderable surface of the water to be exposed to the air, and then 

 added 8 c.c. of the following nutritive mixture : 



Gelatine .......' 20 grammes. 



Dried peptone ... . . 10 



Sodium chloride ....... 10 



Potassium nitrate . . . . . 1 gramme. 



This gelatine, prepared beforehand, is kept in sterilised tubes. 

 Bv adding about 8 c.c. of the nutritive mixture the water is con- 

 verted into a nutritive solution having the following composition : 



Gelatine . . . . . . 2 grammes. 



Peptone . . . > . .1 gramme. 



Sodium chloride ..-.'... 1 



Potassium nitrate . . . . . 0-10 



Water ........ 100 grammes. 



In these flasks the vibrios develop so rapidly that after twelve 

 hours incubation at 37 C. they appear at the surface in the 

 form of a thin pellicle. In order to obtain pure cultures of the 

 vibrios, Sanarelli either plated out loopfuls of the pellicle in 

 gelatine, or made several passages through the gelatine and 

 peptone water, re-inoculations being made every six hours. In 

 this way absolutely pure cultures were obtained, the vibrios 

 appearing before the water bacteria had time to develop. 



THE VITALITY OF THE CHOLERA SPIRILLUM IN WATER, &c. 



A large number of experiments have been made to ascertain 

 the vitality of the cholera spirillum in water. Kraus studied 

 the behaviour of the spirillum in three specimens of water 

 which had the following chemical composition : 



T ?. t f 1 Chlorine. Xitr.ites. Nitrites. Ammonia. 

 (All in parts per 100,000.) 



No. 1. Pipe-supply . 27'0 0'41 0'2-i 0'036 



No. II. Well-water . .V.H5 2-<7 ;)<; 0'304 



No. III. Well-water . 5G-0 2 :>("> 0'26 trace 0-020 



