The Nitrifying Ferments of the Soil. 
707 
gular in their mode of growth as to differ from all living organ- 
isms previously known. 
When a chemical transformation is carried on by the agency 
■of a living ferment (as the fermentation of sugar into alcohol by 
the yeast plant), the vital nature of the process is clearly pointed 
out by symptoms which a few very simple tests suffice to dis- 
close. The symptoms which led to Schloesing and Miintz' 
conclusion were the stoppage of nitrification by antiseptics, and 
the power of provoking it in a suitable medium by simple inocu- 
•lation with soil. Sewage, as is well known, contains ammonia, 
■ and one of the principal actions taking place when sewage is 
I purified by irrigation or filtration through soil is the nitrifica- 
tion of this ammonia. The French observers, experimenting on 
the purification of sewage, were filtering it through a mixture of 
sand and limestone. Not until twenty days did any nitrification 
take place, but then the material nitrified the sewage completely 
and continuously for four months. But on exposing the filter- 
ing medium to the vapour of chloroform (which is fatal to 
' microbes) niti-ification stopped, nor, after sweeping away all trace 
of the chloroform by a fresh current of sewage, was the process 
found to commence afresh, even after seven weeks' trial. The 
filtering column was then inoculated or seeded by pouring on it 
a few scruples of garden soil suspended in water, and eight days 
after this the current of sewage was nitrified as at first. 
This striking result determined Warington to take up the 
study in the llothamsted laboratory, with the immediate result 
, of proving that bisulphide of carbon and carbolic acid, two other 
i antiseptics, are, like chloroform, inimical to nitrification, and 
that darkness favours it, as it does many other bacterial pro- 
cesses. He also showed that dilute solutions of ammonia salts 
I supplied with small quantities of plant food readily nitrify when 
: inoculated with garden soil or with a few drops of a solution in 
which nitrification has commenced, but do not do so when this 
I inoculation is omitted, 
I Experiments on such nitrifying solutions form the basis of 
most of Warington's investigations on the subject, which are 
detailed in a series of connected papers appearing in the 
Chemical Society's Journal in 1878, 1879, 1881, and 1891, and 
in papers dealing with separate aspects of the question appear- 
ing in 1885, 1887, and 1888. Facts in abundance, all con- 
firming the ferment theory of nitrification, were soon adduced 
by him and by other experimenters. Thus the boiling of a 
solution after inoculation is sufficient to prevent nitrification 
altogether, and to stop it if it has commenced. Such a boiled 
solution may be kept for years without change provided the dust 
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