The Micro-organisms of the Soil. 
847 
and Muntz were the first to observe nitrifying ferments, but to 
Warington and Winogradsky belongs the credit of isolating the 
nitrous from the nitric ferment ; furthermore, the striking discovery 
of a colourless organism, capable of existing and performing its 
functions in a medium totally devoid of organic material, and 
synthetically producing organic bodies independent of sunlight. 
The importance of this discovery cannot be over- estimated. 
Warington succeeded in obtaining oi’ganisms from meadow soil, 
cultivated in a solution of ammonium chloride and calcium carbo- 
nate, which oxidised ammonia to nitrous acid, but had no eflfect 
on nitrates. Assimilating the carbon of the carbon-dioxide, they 
require no organic substance for sustenance. They obtain from the 
oxidation heat of ammonia the necessary energy to dissociate or 
break up the carbon-dioxide. 
Winogradsky obtained the same ferment, employing 1 gramme 
ammonium sulphate, 1 gramme potassium phosphate, dissolved in 1 
litre Zurich water, to which he added basic magnesium carbonate. 
After inoculating the sterilised fluid with the nitrifying agent, every 
trace of ammonia disappeared the fifteenth day. He describes this 
ferment as being in shape an elongated ellipsoid. The organisms 
congregate about a piece of carbonate, cover it with their gelatinous 
mass, and as the carbonate disappears the cells take the shape 
thereof. 
Although the two investigators do not quite agree as to the 
morphological attributes of the ferment, Warington arrived at the 
same conclusions as Winogradsky. 
Winogradsky has at last succeeded in isolating the ferment 
which converts the nitrites into nitrates. He employed gelatinous 
hydrate of silica, and impregnated it with a fluid containing the 
cultivated nitrous ferment. This medium was next inoculated with 
strongly nitrifying soil from Quito ; shortly aftei’wards two difierent 
organisms formed respective colonies, one of which was the one 
sought for. It was composed of irregularly shaped rods, dissimilar 
to the nitrous fennent of the same soil. He has since found this 
ferment in many other soils ; it is capable of converting solutions of 
nitrites into nitrates. 
Strange to say the isolated ferment from Quito does not oxidise 
ammonia ; it produced neither nitrites nor nitrates when sown in 
ammoniacal fluids, easily nitrified by the nitrous ferment. 
In normal soils the nitrate ferment only produces nitrates even 
in the presence of a large quantity of ammonia, which does not 
I’etard the oxidation of the nitrites immediately after their for- 
mation. 
Muntz claims the existence of an ammoniacal ferment in the soil 
which converts organic nitrogen into ammonia, preparatory to 
nitrification. 
Extra-cellular Action . — In order to oxidise outside of the or- 
ganisms, oxygen must be evolved by an a.ssimilation process. As- 
similation as an oxidising cause, for conditions prevailing in the 
soil, has heretofore attained no significance, since the evolution of 
