46 THE FORMATION OF PROTEIDS IX PLANT-CELLS. 



di-ammonium phosphate. IJ After addition of the organic 

 nutrient to be tested, the liquids are inoculated with bacteria. 

 In those cases, in which the growth of a specific bacterium has 

 to be tested, a previous sterilisation is of course necessary. 

 An incipient turbidity, the formation of flocculi or of a thin 

 film and the microscopical examination will very soon indicate 

 that the bacteria have grown and multiplied. Organic bases 

 are best neutralised with phosphoric acid, while acids are best 

 applied as sodium salts. 



It is, however, not only of interest to decide, which combina- 

 tions can serve for nutriment, but also to elucidate the reasons, 

 why often closely related compounds behave far differently 

 from each other, and why certain substances, which are in 

 neutral solution by no means poisonous, cannot be used as 

 food. We find for instance that pyridin, pinacon, dimethyloxy- 

 pyrimidin, ethylendiamin, amidoacetal, glyoxal, meconic acid, 

 oxalic acid in dilutions of 0,5% do not support bacterial growth, 

 and acetoxim, diacetonamin, citraconic and maleic acid permit 

 only with difficulty after a series of weeks a gradual develop- 

 ment. 2) These compounds are therefore not well suited for 

 the preparation of those atomic groups that serve for the 

 formation of proteids. Control experiments with addition of 

 0,2% peptone indicated, by the rapid development of bacteria, 

 that neither of these substances are poisonous in such a degree 

 as to kill the bacteria if well nourished. 



The fact that fumaric acid supports bacterial life so well, 

 that a few days after the infection the liquid swarms with 

 numberless bacteria, while it takes 4 weeks with the isomeric 

 maleic acid before a slow development, after repeated infection, 

 takes place is of biological interest. Whether here a gradual 

 adaptation took place or only specific germs were developed, 

 remains to be decided. In the case of citraconic acid no 

 development for six weeks was observed ; finally, after repeated 

 infections a scanty vegetation set in, consisting of apparently 

 only one kind of bacterium, forming short thick rods often in 



1) Calcium salts are not necessary for the life and development of the lower 

 fungi, Compare O. Loew, On the functions of calcium ?.nd magnesium salts in 

 plants, Flora i8g2. 



2) O. Loew, Centr. f. Bacteriol. 22, 361 



