( 153 ) 
In 1897 WersseNBerG ') pronounced the hypothesis, that, at the redue- 
tion of nitrate to free nitrogen, nitrite constantly appears as inter- 
phase. I ean perfectly well share this view, and that for the following 
reasons: 
1st. All denitrifying species which I have studied in the course of 
this research could, in as much as they produced free nitrogen from 
nitrate, do the same from nitrite. 
2nd. Like Burrt and Srurzer (l.c.) I have been able to isolate a 
species, which does convert nitrite into free nitrogen, but leaves 
nitrate intact, so that from a mixture of nitrite with a little nitrate, 
all the nitrite is removed by this bacterium, whilst the nitrate remains 
unchanged. 
Here I must however observe, that at the conversion of nitrate into 
free nitrogen, not always nitrite can be detected in the culture. ‘This 
fact has already been stated by SewerIN ®) and KÜNNEMANN *). It is 
however by no means in contradiction with WersseNBerG’s hypothesis, 
for if the course of the second process: decomposition of nitrite, is 
quicker, or as quick as the first : reduction of nitrate, the nitrite-phase 
is no more to be demonstrated. 
Ktnnemann observed this fact in a variety of B. stutzeri’, which 
observation I have been able to confirm ; however, in my opinion, the 
cultural conditions played in this experiment a much more important 
part than the character of the variety. In bouillon with 0,1 °/, KNO,, 
I could often point out no nitrite, whilst here a strong development 
of gas took place. On the other hand, I obtained with 4 and 5 °/, 
KNO, only a slight gas development, but a strong reaction of nitrite. 
For the investigation of a colony on its denitrifying power, sterile 
test-tubes were filled with 10 a 15 Cem. of bouillon, as well with 
0,1°/, KNO, as with 0,1 °/, KNO, and then inoculated. Denitrifying 
bacteria grow therein sufficiently, after 24 hours to produce a distinet 
turbidity, whilst, at the surface they form a scum-layer. Sometimes 
the scum is wanting, but is produced at shaking the test-tube. 
Besides were used solutions of calcium-salts of organic acids, decocts 
/, cane-sugar, and decocts of potatoes, likewise 
with 0,1 °/, KNO, or KNO, 
In this case a control experiment was made to decide, whether 
of pease-leaves with 2 °/ 
without addition of nitrate or nitrite, these solutions might cause 
1) Studien über Denitrification. Arch. f. Hygiene. 1897, Bd. 30, 5. 274. 
2) Zur Frage über die Zersetzung von Salpetersauren Salzen durch Bakterien. 
Centrbl. f. Bakt. Abt. II, 1897, Bd. 3, S. 504. 
3) Ueber denitrifizierende Mikro-organismen. Landw. Versuchs-Stat. 1898, Bd. 
50, S. 65. 
