THE NITRIFYING PROCESS AND ITS SPECIFIC FERMENT. 
121 
organisms to deal with ; the one causing nitrification, but refusing to grow in the 
gelatine, the other growing in the gelatine, but incapable of producing nitrification, 
(3n this hypothesis bottle No. 1 contained the nitrifying organism in a state of purity, 
bottle No. 2 the non-nitrifying organism also in a state of purity, whilst bottle No. 3 
contained a mixture of the two organisms. This supposition was the more probable 
as the less highly attenuated, and therefore presumably less pure, bottle No. 5 
(dilution ttw^Wo)’ bottles Nos. 10 and 12 (dilution r.ooo7oMo)j of which had 
nitrified, yielded growths on being inoculated into gelatine-tubes. 
These observations were confirmed both by repetition and by the pouring of gela¬ 
tine-plates from bottles Nos. 1 and 5, the plates from No. 1 yielded no colonies what¬ 
ever, whilst those from No. 5 showed numerous small colonies. 
It was thus established, beyond doubt, that the bottle No. 1 had nitrified, that it 
contained numerous micro-organisms of a very short bacillar form, but that this 
organism coidd not be cidtivated on gelatdie-peptone. 
We next endeavoured to continue the cultivation of this organism in the 
ammoniacal solution, in order to ascertain whether it retained its nitrifying power, 
as well as its property of refusing to grow in gelatine. 
Accordingly, on June 28, 1889, five bottles containing sterile ammoniacal solution 
were inoculated with a needle from bottle No, 1. These bottles, which may be 
described as No. 1 (2nd generation), were kept in the dark, at the temperature of 
the air, during the long vacation, and examined on October 18, 1889. Tlwy were cdl 
five found to have strongly nitrified, but on inoculating them resgoectively into 
five different gelatine-tubes, in no single case was a groioth develojyed. 
By way of control we had on the same day inoculated a gelatine-tube from the 
23rd generation of the direct series experiments referred to on page 113, and this 
tube had already on the third day developed a visible growth. 
On microscropically examining these five bottles (No. 1, 2nd generation), we again 
found in each case the characteristic small, almost micrococcus-like bacillus, to which 
we have had occasion to refer so frequently before, and which we may nov/ fitly 
describe more in detail, having by the above experiments clearly established its causal 
connection with the process of nitrification. 
Characterisation of the Bacillus of Nitrification. 
(1) We have noticed that the solutions which had undergone nitrification by the 
organism in question remained perfectly clear, whilst the solutions which suffered 
nitrification by the mixture of organisms present in the direct series of experiments 
(see p. 113), generally exhibited a thin surface-film, and sometimes slight opalescence. 
(2) One of the nrost remarkable features of the organism is its capacity of 
apparently indefinite growth in a medium practically destitute of organic matter, 
MDCCCXC.-B. 
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