Robert Warington. | XX8 
of one organism itself; and to prepare himself for this task Warington wenf 
to London for a time, in 1886, to learn bacteriology under Dr. Klein at the 
- Brown Institution. From Dr. Klein he obtained a large number of pure 
cultures of various bacteria, and all these, as well as others obtained from his 
own experiments with soils, he examined as to their behaviour towards 
ammonia and nitrates, and also as to their mode of growth on skim-milk. 
The results were brought before the Chemical Society, and proved that none 
of the bacteria, except the nitrifying organism itself, possessed any appreciable 
power of nitrification. The majority of the organisms examined, however, 
were active denitrifiers. Denitrification—whereby nitrates are converted into 
nitrites, oxides of nitrogen, or even nitrogen gas—was, at this time, a well 
recognised work of micro-organisms, but was one which, naturally, enhanced 
to a considerable extent the difficulties met in elucidating the reverse 
phenomenon of nitrification. Warington’s work added a good deal to our 
knowledge of the subject, and showed that denitrification is a property 
actively exhibited by a large number, but by no means by all, micro-organisms, 
and that in a soil it becomes complete, before the nitrifying organisms 
begin their task of reversing the reaction. An excellent account of the 
denitrification of farmyard manure was subsequently written for the ‘Journ. 
- Roy. Ag. Soc.,’ 1897, vol. 8, Part IV. 
Warington’s work on nitrification was amply sufficient to establish the fact 
that the oxidation of ammonia in the soil was the work of an organism, but 
that organism seems to have been isolated first by Schloesing and Miintz in 
1879, though the method which they adopted left, at the time, considerable 
doubt as to its real identity. But even the isolation of this organism did 
not solve the whole problem: there was still the independent formation of 
nitrites and nitrates to be accounted for; and it was here that Warington’s 
work was most conducive to a solution of the difficulties, for he succeeded 
in proving that one organism alone could not be held accountable for the 
various phenomena observed, and that two different organisms must be 
concerned in the process of nitrification. His success all lay in the chemical 
aspects of the subject. He was the first to obtain (1879) liquid cultures 
which converted ammonia into a nitrite, and preserved this power in all 
sub-cultures, but which was incapable of producing any nitrate ; and shortly 
afterwards (1881) he obtained cultures which were able to convert nitrites 
into nitrates, but were unable to oxidise ammonia. This was a practical 
separation of two distinct organisms, but at the time Warington did not 
grasp the true meaning of his results, and he associated the change from 
nitrites into nitrates with a white growth which appeared floating in 
the liquid, but which really had nothing to do with it. 
In 1890, after the work of others had resulted in the isolation of the 
nitrous organism (that which converted ammonia into nitrites), Warington 
returned to the subject, and found that the white surface organism could not 
be held accountable for the conversion of the nitrites into nitrates. He 
eventually succeeded in isolating the organism which really produces this 
