BY R. GREIG SMITH. 751 



at a later date with the equivalent of 2000 c.c. of water was like- 

 wise found to be sterile. This fact is rather curious, because a 

 culture of Bact. coli commune isolated from faeces grew to a 

 considerable extent in the medium at 42°. It probably indicates 

 that the varieties of Bact. coli that are present in the water (and 

 a variety was found in 800 c.c. on the same date as the repetition) 

 are considerably weakened, so much so as to b« unable to grow 

 in Jordan's medium at 42° C. 



With a water temperature of 13° C. (end of August) no 

 growth was obtained in tubes containing 7 drops of Parietti's 

 solution to every 10 c.c. of a mixture of bouillon and bacterial 

 suspension, even when the equivalent of a litre of water was 

 employed. Growth was obtained later in the year (middle of 

 October) when the temperature of the water had risen to 17° C. 

 To tubes containing 10 c.c. of bouillon were added 1*5 c.c. 

 portions of bacterial suspension (representing 300 c.c. of water) 

 and from 1 to 6 drops of Parietti's solution. The tubes were 

 incubated at 37° C. A turbidity and surface film appeared in 

 each, and as time went on the film became black. Plates which 

 were infected with the 4 and the 6 drop growth produced colonies 

 which appeared like drops of gum. This organism was proved to 

 be Bac. mesentericus niger, Lunt, a recently discovered potato 

 bacillus. Using the same quantities of bouillon and bacterial 

 suspension growth occurred in the presence of 9 drops of Parietti's 

 solution, but 9 drops appeared t© be the limit for the quantity of 

 suspension employed, as the tube with 10 drops remained clear. 

 With regard to the ratio between Parietti's solution and the 

 infected medium, the dropping pipette delivered 36 drops to the 

 c.c. (grm.) and the bouillon mixture measured ITS c.c The 

 plates that were prepared with the cultures in the 7 and 9 drop 

 tubes produced what appeared in each case to be a pure culture 

 of Bacterium I. This organism appears to be Bac. aquatilis 

 communis. In a test made at a later date, when the temperature 

 of the water had risen to 22° C, colonies of Bact. coli commune 

 were found in plates which had been prepared from a 24 and a 

 48 hours' culture in 8 drops of Parietti's solution per 10 c.c. of 



