104 BACTERIOLOGY. 



rent conception, to nourish themselves solely 

 upon organic substances by the breaking down 

 of these substances. Dujardin, however, as 

 far back as 1841, discovered that bacteria can 

 build up their body-substance out of am- 

 monium oxalate. Oxalic acid is C 2 H 2 O 4 = 

 COOH.COOH, so that no formation of for- 

 maldehyde can occur through a simple re- 

 arrangement of the atoms. With the forma- 

 tion of the amido group, what probably happens 

 is that since the oxalic acid in question is an 

 ammonium salt, a reduction by the hydrogen 

 of the ammonia occurs : 



2NH 3 = 2NH 2 + H 2 

 ammonia, amido group, hydrogen. 



COOH.COOH + H 2 CHOH + CO 2 + H 2 O 



oxalic acid, hydrogen, formaldehyde. , 



The further synthesis of proteid can after- 

 wards proceed out of the formaldehyde and the 

 amido group. 



Again, formic acid cannot pass over into 

 formaldehyde simply by atomic rearrange- 

 ment, and yet O. Low has made the important 

 discovery which rounds out this series of obser- 

 vations, that a bacterial species which can turn 

 formaldehyde to account in constructing its 

 oody-substance can also make use of formic 

 acid. Formic acid is CH 2 O 2 . Since it pos- 

 sesses both acid and reducing properties its 



