THE EQUATION OF LACTIC FERMENTATION. 225 



found by ESCHERICH (I.) in the contents of the intestines of 

 sucklings, and also in uncooked cow's milk, were investigated by 

 A BAGINSKY (II.), who found that in artificial media containing 

 lactose it produces both acetic acid and lactic acid. The gas 

 liberated during the reaction consisted of C0 2 , 22 per cent.; 

 H, 30 per cent; CH 4 , 9 per cent.; N, 39 per cent. K. WURTZ 

 and R. LEUDET (I.) considered this microbe to be identical with 

 Pasteur's lactic acid bacillus, but their opinion does not seem to 

 be well founded. According to J. DENYS and J. MARTIN (I.), 

 B. lactis aerogenes is only a variety of the Pneumobacillus (33) 

 discovered by Friedlander. 



Respecting the Pediococcus acidi lactici discovered by P. 

 LINDNER (I.) a few particulars will be given in Chapter xxv. ; and 

 details concerning the part played by the lactic acid bacteria in 

 certain industrial fermentation processes, such as distilling, dairy- 

 ing and cheese-making, tanning, &c., will be found in Chapters 

 xxiii. to xxvii. 



136. The Equation of Lactic Fermentation 



is (when lactose or grape-sugar is presupposed as the raw material) 

 generally expressed in chemical text-books as follows : 



H 2 = 4C 3 H 6 3 

 Lactose. LacticJAcid] 



C 6 Hi 2 6 = 2C 3 H 6 3 . 



Actually the process is not so simple as here represented, a 

 certain quantity of the sugar employed being consumed by the 

 organisms to enable them to discharge their vital functions and 

 bring about the fermentation in question. Consequently the actual 

 yield of lactic acid obtained is less than the theoretical quantity 

 calculated from the foregoing equations. Another proof of the 

 complex nature of the operation is afforded by the large quantity 

 of gas liberated during the fermentation, but which is not indicated 

 in the reaction expressed by the equations aforesaid. 



According to the researches of R. WARINGTON (I.),, the amount 

 of acid produced varies greatly in different species, and is so small 

 with some that (as noted by Conn) it is insufficient to curdle the 

 milk. This difference is explicable by the varying susceptibility 

 of the individual species to the adverse influence of the resulting 

 acid. On this account alone, fermentation may come to a stand- 

 still notwithstanding the presence of sufficient unconsumed nutrient 

 material. The difficulty is easily met by opportunely neutralising 

 the acid by an addition of the carbonate of calcium, magnesium, 

 or zinc. In the latter case, the highly characteristic lustrous 

 acicular crystals of zinc lactate ( [C 3 H 5 3 ] 2 Zn + 3 aq.) are obtained. 



VOL. I. P 



