THE NITRIFYING PROCESS AND ITS SPECrFIC FERMENT. 
Ill 
indicated that a very different interpretation should be put ipjon Herteus’s results to 
that which he had himself suggested. 
The indications of nitrous acid which he had obtained on growing these organisms 
in diluted urine were obviously due to reduction of the small quantity of nitrates 
almost invariably present in normal urine, and not to any oxidation of the ammonia 
at all. This was pointed out by one of us in the paper in question, and, of course, 
casts a suspicion also upon the supposed nitrification obtained by Hera:us with the 
pure cultures p, cr, (j), and y, to which we had no access. 
In further endeavours to obtain nitrification by means of pure cultures, one of us 
experimented witli no less tlian 33 different forms obtained by us from air and water,''' 
but in every case tlie results were negative. Such a number of negative results 
obtained when working under precisely similar conditions to those indicated by 
Heiia:us naturally tended to shake our belief in his having ever obtained more than 
traces of nitrous or nitric acids in any of his experiments with pure cultures. 
Note. —Of other investigations professedly made with pure growths the following 
may be mentioned :— 
“ Nitrification,” A. Celli and F. Marino-Zuco (‘ Gazz. Chim. Ital.,’ vol. 17, 
pp. 99-103; ‘ Chem. Soc. Journ./ Abst., 1887, p. 858), in which the authors claim 
to have found a micrococcus {M. cereus) which behaved as a very efficient nitrifying 
agent. They further mention preliminary experiments purporting to show that 
certain organisms (B. saprogemis, B. JiuidiJicans, and M. hiteus) destroy nitrates 
when takeir from gelatine, but produce nitrates when taken from potato-cultures. 
“ Changes induced in Water by the Development of Bacteria,” T. Leone (‘ Gazz. 
Chim. Ital.,’ vol. IG, p. 505 ; ‘ Chem. Soc Journ.,’ Abst., 1887, p. G15), in which the 
author asserts that the same organisms may successively produce nitrification and 
'reduction of nitrates according to circumstances. 
“The Chemical Action of some Micro-organisms,” li.' Warington (‘Chem. Soc. 
Journ.,’ 1888, p. 751). In this paper the author records his failure to produce 
nitrification with pure growths obtained by gelatine-plate culture from nitrifying 
solutions; he reviews the present position of the question of nitrification, and con¬ 
cludes with the words “ an organism which nitrifies as soil nitrifies has yet to be 
isolated.” 
Failing to obtain nitrification with any of the pure cultivations of organisms in our 
collection, we determined to approach the mattei’ from a different side, viz., to induce 
nitrification by a mixture of organisms, and then from tliis nitrifying mixture to 
attempt to isolate the particular organism or organisms responsible for the process. 
* “ Studies on some New Micro-organisms obtained from Air,” by Grace C. Franklanu and Percy 
F. Franklaxd, ‘Phil. Trans.,’ 1887, ii. 2.57; also “ Ueber einige typische Mikro-organismen im Wasser 
und im Roden,” by the same, ‘ Zeitsch. f. Hygiene,’ vol. 6, 1889, p. o73. 
