54 
THE FORMATION OF PROTEIDS IN PLANT-CELLS. 
of nitrogen, the latter has to be split off in shape of ammonia, 
before the protein formation can begin. This can be accom¬ 
plished in many cases by simple splitting (acetamid, kreatin, 
urea, etc.), in other cases by oxidation, as with leucin, methyl- 
amin, betaïn. Chinin and strychnin are poor sources of 
nitrogen, being attacked by fungi with difficulty, and antipyprin 
and dimethyl-oxypyrimidin offer so much resistance, that their 
nitrogen cannot at all be utilised. 
The anaerobic microbes may by reducing influences transform 
nitrogen of certain compounds into ammonia, while the aérobic 
employ oxidation : 
1) H 2 N.CH 2 .COOH + 2H = NH 3 + CH 3 .COOH, 
2) H 2 N.CH 2 .C 00 H + 3 0 = NH 3 + 2C0 2 + H 2 0 . 
A very remarkable case is the assimilation of free nitrogen 
by certain bacteria of the soil as was asserted years ago by 
Berthelot T) and recently confirmed by Winogradzki. The free 
nitrogen is here probably first converted into ammonium 
nitrite, * 2) 3 and the nitrous acid then also rapidly reduced to 
ammonia. 
The proteids of mould-fungi and of yeasts 3 ^ contain, like the 
other proteids, sulfur which can partially be split off by diluted 
alkaline ley in form of sulfide ; the sulfur must therefore be in a 
very loose form of combination, very probably present as—SH 
in the proteins. Sulfates have to be reduced therefore to sulfuret- 
ted hydrogen, before the sulfur can be assimilated, and organic 
sulfur compounds have to be split before reduction and assimi¬ 
lation take place. My experiments with sulfonal (CH 3 ) 2 : C: 
S 0 2 (C 2 H 5 ) 2 have shown that this substance serves well as a 
source of sulfur for mould-fungi and yeasts, in the presence of a 
good source of carbon ; but in the absence of such a source, sul¬ 
fonal cannot be used, although it contains the methyl and ethyl 
group, i.e. otherwise good sources of carbon ; the fungi refuse to 
x) Compt. rend. ioi. —Also Gautier and Drouin , Ibid, 106. 
2) About this transformation with the aid of platinum black, see O. Loew , Ber. 
Deutsch. Chem. Ges. 23, 1444. 
3) Ncncki found in 2 cases no sulfur in the proteids of bacteria. 
Mitscherlich found in yeast 0,6 o[ 0 sulfur. If yeast be treated with a diluted 
solution of caustic potash, a considerable amount of potassium sulfide is formed. 
