358 CHEMICAL ACTIVITY OF ASPERGILLACE^. 



those of EMMERLING (VI.) and HEINZE (II.). We have naturally 

 excluded here the cases in which the production of oxalic acid is 

 regulated by the liberation of bases during metabolism (e.g., the 

 salts of other organic acids, amides, peptones, &c., are consumed). 

 In such cases oxalates are produced instead of any surplus of free 

 acid, the process here which is independent of temperature 

 being of a different character, and in the absence of the liberated 

 bases no accumulation of acid would take place. To this class of 

 process relate several earlier and later investigations mentioned 

 in the literature, where the workers, e.g., ZOPF (XIV.), BANNING 

 (I.,) &c., employed additions of amides, peptones, meat extract or 

 gelatin, instead of merely sugar solutions and mineral salts. In 

 presence of actively oxidising organisms, the chemical nature of 

 these substances necessarily entails the formation of oxalates or 

 carbonates. Up to the present, no competitor exhibiting the same 

 decided peculiarity as Asp. niyer has been found among the thread 

 fungi, yeasts or bacteria. 



A work on the production of oxalic acid by Asp. niger, pub- 

 lished in 1905 by CHARPENTIER (I.), who was unfortunately not 

 acquainted with the existing literature of the subject, merely 

 repeats what was already well known ; and his remarkable con- 

 clusion that the production of acid is a result of the exhaustion 

 of the nutrient medium shows such an inaccurate conception of 

 the true state of affairs as to require no serious refutation. 

 According to HEINZE (II.), acetic acid is formed along with the 

 oxalic acid a statement requiring further confirmation, at least 

 so far as pure cultures are concerned. In view of the ease with 

 which acetic acid is decomposed by the fungus in question, as 

 reported by PFEFFER (VI.) and DUCLAUX (XXII.), this formation 

 is not very probable, nor has it been properly demonstrated. 

 Moreover, the circumstance that Heinze's three experiments 

 with a two-fold and three-fold quantity of nutrient solution, the 

 amount of oxalic acid was correspondingly greater than with 

 200 c.c., is as emphasised by Wehmer the natural result of 

 the regulation of the production of acid, and not due to the 

 lower content of nitrogen. That Heinze observed the formation 

 of potassium nitrate by this fungus from peptone, gelatin, &c., 

 is incredible from the sum of his reports. The brief statements 

 of KOSTYTSCHEW (I.) regarding the production of acid by the 

 intramolecular respiration of Aspergillus are of too general a 

 character to allow definite conclusions to be drawn from them. 



Citric acid fermentation ranks along with that in which 

 oxalic acid is produced, and relates solely to the formation of free 

 citric acid, but not to the production of citrates so generally 

 observed among the phanerogams and fungi. A parallel to the 

 exciters of this fermentation is found among the phanerogams, 

 in the Citrus species, just as Aspergillus niger is physiologically 

 allied to the Rumex and Rheum species. We shall now deal con- 

 cisely with the chemistry conditions and course of the process, as 



