178 Tannic Acid Fermentation 



lation of more sugar but by a stimulus, the result of high concen- 

 tration. The table is offered here, however, only to indicate that 

 with the nutrient solution used 5 per cent sugar is not sufficient 

 for greatest growth. It throws light also upon the failure of the 

 5 per cent sugar to protect the gallic acid in the previous experi- 

 ment. 



VII. ELECTION OF ORGANIC SUBSTANCES. 



Historical. VanTieghem" stated that the glucose formed as a result of 

 tannic acid fermentation was utilized and the gallic acid left behind. Pas- 

 teur demonstrated that Penicillium glaucum exhibited an election of the 

 dextro-tartaric acid when both the dextro- and 1 ae vo-tartaric acids were 

 present. Duclaux's'^ observations revealed the fact that when Aspergillus 

 niger was offered salts of butyric and acetic acid in a mixture, it first used 

 the latter and then the butyric acid. Furthermore, he proved that this 

 was not due to the better nutrient value of acetic acid, for when the acetate 

 was offered with the tartrate (an especially good nutrient) the acetate was 

 utilized more rapidly. The election then was not merely a matter of rela- 

 tive food value. 



Pfeffer^' found that under certain conditions the use of glycerin by fungi 

 may be protected by dextrose and even better by peptone, and he showed 

 also that the relative concentration of each had an effect upon the election. 



Puriewitsch'' found with two organisms an election with respect to the 

 products of amygdalin. With this substance as the source of carbon it 

 was first transformed; then the dextrose and lastly the benzaldehyde was 

 used. He found further that salicin was not transformed in the presence of 

 six times its quantity of dextrose, twelve times its quantity of saccharose 

 or fourteen to sixteen times its quantity of starch. 



Election of cane sugar. In order to determine definitely whether 

 or not Aspergillus niger and Penicillium sp. elect cane sugar, when 

 it is offered together with gallic acid, two series of cultures were 

 made. Solution B was used, to which was added in the one case the 

 gallic acid and 10 per cent of cane sugar, the cultures being made 

 in Erlenmeyer flasks as before. In a similar manner cultures 

 were made in which the gallic acid alone was offered as the source 

 of carbon. Sterilization and inoculation were made by the usual 



'* Loc. cit. 



5«E. DuClaux: Sur la nutrition intracellulaire, Ann. de I'Inst. Pasteur 

 iii, pp. 97-112, 1889. 



" W. Pfeffer: Ueber Election organischer Nahrstoffe, Jahrb. f. wiss Bot 

 xxviii, pp. 205-268, 1895. ' 



'* Loc. cit. 



