IIG 
PROFESSOR P. F. FRARKLAND AND MRS. G, 0. FRANKLAND ON 
After a preliminary microscopic examination with a view to roughly estimating the 
number of micro-organisms in a given volume of the liquiclj the following process of 
dilution was carried out :— 
First Dilution 
(1 drop in 50 c.c. 
of sterile water). 
No. 1 bottle inoculated with 1 drop (= xoho (^I’op of original nitrifying solution). 
No. 2 bottle ditto. 
No. 3 bottle inoculated with 1 drop (= i,oohooo di’op of original). 
No. 4 bottle ditto. 
No. 5 bottle ditto. 
No. 6 bottle inoculated with 3 drops (= i.b ' oo.o oo drop of original). 
No. 7 bottle ditto. 
No. 8 bottle ditto. 
No. 9 bottle inoculated with 5 drops (= drop of original). 
No. 10 bottle ditto. 
No. 11 bottle ditto. 
No. 12 bottle inoculated with 10 di’ops (= YT^rb^o^oiro drop of original). 
No. 13 bottle ditto. 
No. 14 bottle ditto. 
No. 15 bottle inoculated with 2 c.c. (= TYToodrcTo drop of original). 
No. 16 bottle ditto. 
No. 17 bottle ditto. 
No. 18 bottle inoculated with 5 c.c. (= i.ooo.oob drop of original). 
No. 19 bottle inoculated with 7 c.c. (= i.ooo.ooo drop of original). 
No. 20 bottle inoculated with 10 c.c. (= rTb^oTocTb drop of original). 
The object of this wide range of attenuation was to endeavour to secure nitrification 
in only a part of the series, in which case it would be probable that the most diluted 
bottle in which nitrification still took place had received only one or, at any rate, only 
few individuals of the nitrifying organism. 
These bottles were examined on the 7th July, 1888, when it was found that of the 
three most highly diluted solutions, contained in bottles Nos. 3, 4, and 5, only bottle 
No, 4 had nitrified, whilst bottles Nos. 3 and 5 gave no reactions either with 
diphenyla nine or sulphanilic acid. This, of course, suggested the possibility that 
bottle No. 4 had been nitrified by a pure growth. Two gelatine-tubes were inoculated 
* In all cases in which inoculations were made into gelatine-peptone, the needle was both stabbed 
into the material and also streaked along its surface, with a view to obtaining the depth and surface 
characters of any resulting growth. 
Second Dilution 
(3 drops of First 
Dilution in 50 c.c. 
of sterile water). 
