( 518 ) 
The general occurrence, therefore, of these salts in the soil caused, 
for the following investigations, caleium-compounds of organic acids 
to be chosen in the first place as a source of carbon for ureum- 
splitting bacteria. 
If in a eulture-liquid, containing these salts and ureum, dissolved 
in water to which 0.05 K,HPO, is added, ureum is split, the 
ammonium-carbonate formed will not directly bring about a consi- 
derable increase of alkalinity of the medium, but in the first place 
it will be neutralized by the calciumsalt and that according to 
the formula: 
Ca R + (NH), CO, = CaCO, + (NH,), R 
Therefore the calecium-compounds of the organic acids exercise a 
retarding influence on the alkalinity; for not until all the calcium 
is united with the carbonic acid formed, the alkalinity will advance 
rapidly; then the culture-liquid is like one that contains an ammo- 
niumsalt of an organic acid as source of carbon. This is treated of 
in § 3. 
But it is especially because of the existence of this period of rest 
before the increase of alkalinity, that cultures with calciumsalts of 
organic acids are so particularly fit for the accumulation of less strong 
splitting organisms, by which means every opportunity is afforded 
for study of these kinds, which are otherwise so rapidly supplanted. 
The cause that during this first period also the ureum-splitters 
have the advantage of all the microbes contained in the raw 
infection-material, so that the latter are already then entirely supplanted 
is that their specific source of energy, the urenm, is at their disposal. 
So if we want to get an insight into the numerous kinds of weak 
ureum-splitters, we have to make a plate-culture before all calcium 
is united with carbonic acid. 
As a rule a good result is obtained when after 2 or 3 days the 
plate-making takes place on meat-gelatine or on a culture-medium, 
composed of water, 10°/, gelatine, 0.05°/, K,HPO,, 0.05 NH,Cl 
and 0.5 °/, calc. malate. 
These experiments give a fair idea of the great number of ureum- 
splitting microbes which the soil contains; they follow each other 
as the process proceeds and as the alkalinity increases, till at last the 
strongest, the most powerful hydrolysing kinds are left. 
To give a detailed description of the many weak ureum-splitting 
kinds that exist, would be of hardly any use. 
During my experiments in October, November, and December 1904 
in the Microbiological Laboratory, under the guidance of Prof. 
