REDUCTION PROCESSES. 877 



of sulphur to H 2 S and others, can be brought about by the labile H of the 

 sulphydryl-compounds. In this manner for example the cysteine 

 (see Chapter II) acts and quickly reacts with sulphur with the formation 

 of H2S and similarly acting substances have been detected by HEFFTER 

 in various organs and organ extracts. We have here a group of reductions 

 which are not of an enzyme nature. 



From the investigations of ABELOUS and ALOY 1 it follows that 

 plants as well as animal organs have the ability at the same time of oxidiz- 

 ing salicylaldehyde and of reducing nitrates to nitrites. On the other 

 hand SCHARDINGER, TROMMSDORFF and BACH 2 have shown that fresh 

 cow's milk, which alone is without action upon methylene blue and on 

 nitrates, reduces these bodies in the presence of aldehydes into leucobases 

 or nitrites. Boiled milk does not have this power and the action is 

 explained by the presence of a reductase, the so-called SCHARDINGER 

 enzyme. The optimum of action lies at about 70 C. BACH found the same 

 action in various animal organs. The process may to be just as well 

 considered as an oxidation under the influence of an aldehydase whereby 

 the methylene blue or the nitrate gives up the oxygen for the oxidation 

 of the aldehyde. On the other hand STRASSNER 3 ascribes the reduction 

 of the methylene blue, to the above-mentioned reducing action of the 

 sulphydryl groups. 



1 Compt. Rend., 138, 382 (1904); see also Pozzi-Escot, ibid., 138, 511. 



2 Schardinger, Zeitschr. f. Unters. d. Nahrungs- und Genussmittel, '5, 22 (1902); 

 Trommsdorff, Centralbl. f. Bakter., 49, 291 (1909); Bach, Ber. d. d. chem. Gesellsch., 

 42, 4463 (1909); Bioch. Zeitschr., 31, 443; 33, 282; 38, 154 (1911), 



*Ibid., 29, 295 (1910). 



