THE FORMATION OF PROTEIDS IN PLANS-CELLS. 45 
can be utilised in higher concentration than sodium acetate, and 
this in a higher one than acetic ester or phenol, the latter form¬ 
ing in 0,08 °/ Q solution a meagre food for a micrococcus,although 
in higher concentrations a poison for all kinds of bacteria. The 
more easily a compound is attacked by the cells, the quicker the 
development of new cells. 
As sources of carbon : alcohols, acids, ketons, aldehydes, 
carbohydrates, esters and bases can serve. As sources of nitrogen : 
nitrates, ammonium salts, amido-acids, ureas, guanidins, nitriles, 
amines, ammonium bases can serve. As sources of sulfur may be 
utilised not only sulfates but also organic sulfur compounds, as 
sulfons, sulfonic acids and probably also sulfides (methyl sulfide). 
Our observations in regard to the sources of carbon teach us :— 
1) The nutritive quality of acids is enhanced by the en¬ 
trance of alcoholic hydroxyl-groups ; thus lactic acid is superior 
to propionic acid. 
2) The nutritive value of alcohols is increased with the 
number of the hydroxyl-groups : gtycerin is better than propyl 
alcohol. 
3) The presence of aldehyde-or keton-groups increases the 
nutritive qualities : glucose is better than mannite ; acetyl acetic 
ester is better than acetic ester. 
4) The lower alcohols may be used in higher concentration 
than the higher ones (amyl alcohol). 
5) The lower members of the fatty series are more easily 
assimilated than the higher members ; sodium acetate being far 
superior to sodium valerianate. 
6) The unsaturated ring systems are generally not favora¬ 
ble ; for instance antipyrin and dimethyloxypyrimidin appear 
to be entirely unsuitable and while benzoic and salicylic acid 
are very poor sources of carbon, phenyl acetic acid, containing a 
CH 2 group, is far better, and chinic acid, containing a saturated 
benzol-ring with 4 CHOH groups is a very good source. 
To carry out such experiments, mineral solutions are 
prepared containing 0,1—0,5% dipotassium phosphate, 0,01— 
0,05% magnesium sulfate and 0,1—0,2% potassium nitrate or 
1) Compare Ncigeli , Ber. Bayr. Akad. d. Wiss. 187g. 
2) I have here operated with 0,1 o/ 0 solutions. Biol. C. 10, 585. 
