1053 
the nature of the metabolism of the carbon, but does modify its 
velocity and that substitution of rubidium to potassium neither changes 
that nature. This I have also found true for the nitrogen under the 
influence of the said metal, as is shown in table III. 
Nr. 2, where manganese is added, has a lower nitrogennumber than 
1, which is owing to the manganese. The nitrogennumbers of 7, 8, 
and 9, are lower than those of 8, 4, 5, and 6, where no manganese 
is added. The nitrogennumber of 10 is like that of 3, 4, 5, and 6. 
The addition of 0,00l mgr. zinesulfate (ZnSO,.7 Aq.) changes neither 
the metabolism of the nitrogen nor that of the carbon. *) 
That the replacing of potassium by rubidium has little influence on the 
metabolism of “the nitrogen is proved by comparing nrs. 11 and 12 
with 3, 4, 5, and 6, and 19 with 18, whose nitrogennumbers are 
nearly equal. | 
In the above deseribed experiments the nitrogen in the liquid was 
of different nature, both in the form of ammonium and of nitrate. 
For that reason I repeated the experiment and used ammonium- 
chiorid as only source of nitrogen. 
Various concentrations were also studied. The results are found 
in-table EV. 
From these experiments we may conclude that the nature of the 
metabolism with ammoniumehlorid is the same as with ammonium- 
nitrate. The nitrogennumber, high at first (6,1), descends rapidly ; 
after 7 days it is already decreased to + 2,5, then to remain nearly 
constant. Furthermore we see that excess of nitrogen does not change 
the metabolism. All the nitrogen excreted is found exclusively as 
ammonium, the sum of the nitrogen in the mould and of that present 
in the solution being constant. The losses of nitrogen which may 
partly be aseribed to errors in the analysis, are, as seen in the table, 
of little import, and partly repose on the evaporation of ammonia. 
Thus we see that in the till now examined cases ammonia is a 
normal excretion product in the metabolism of Aspergillus niger. 
After Prof. BöÖrSRKEN's advice I investigated if this is always 
the case; if also by nitrogen nutrition with KNO, ammonia is 
excreted. ; 
The results of these experiments are found in table V. We see 
from them that also with. KNO, as exclusive nitrogen food the 
nitrogen is accumulated in the organism, albeit less quickly than 
NH,Cl or NH,NO,. The nitrogennumber lowers also here 
whilst ammonia comes into the culture liquid. There are hardly 
!) These Proceedings, XV p. 760. 
