(514) 
It is for this reason that we have to consider urine, more parti- 
cularly ureum, as one of the most valuable sources of nitrogen for 
arable land. 
Millions of kilogrammes of the indispensable nitrate-nitrogen are 
annually in a biological way formed from urine in the ground and 
are of the greatest use to vegetation. 
Nitrogen taken by man and animal as vegetable albumen, leaves 
the body again for the greater part in the form of ureum, and in 
this way describes a cycle. 
A rough caleulation of the quantity of ureum, which in our 
country is produced by the population and the cattle, gives an idea 
of the enormous quantity of nitrogen describing this cycle. 
The data for the amount of cattle have been taken from Verslagen 
en Mededeelingen van de Directie van den Landbouw. (Reports and 
Communications of the Board of Agriculture). 
The quantity of ureum, daily secreted by the population, amounts 
to + 125000 K.G.; by the cattle = 225000 K.G., making + 350000 
K.G., or + 350 tons a day. 
By biological oxidation, a quantity of nitrate-nitrogen would be 
produced equal to that found in + 900 tons of saltpetre. 
Annually from the + 125000 tons of ureum formed, + 350000 
tons of saltpetre could be produced, representing a value of + 3.5 
millions of £. sterling and this, distributed over the 2155000 acres 
of arable land, would yield + 160 K.G. of saltpetre pro acre. 
That only a trifling part of this enormous mass is utilized for 
agricultural purposes, need not be proved here. Especially in large 
towns for hygienic reasons almost all ureum is lost to any useful 
purpose; on the other hand it would decidedly be of great value 
for farms in the country, to be more careful about collecting urine. 
The above mentioned considerations may serve to draw once 
more attention to the enormous value represented by ureum as a 
manure. 
In the experiments about microbes decomposing ureum the culture 
media generally were characterized by the presence of albumen 
and peptones. 
It is true that von JAKscH *) and BEIJERINCK *) have made experiments 
with salts of organic acids as a source of carbon, but a systematic 
investigation in this direction has not been made as yet. 
Von JAKSCH’s investigation in 1881 was especially of importance for 
1) Zeitschrift fiir Phys. chem. 1881. 
2) Centralbl. f. Bakt. Il, Abt. VII, Bd, 1901. 
