As a matter of fact this substance cannot be detected among the products of fermentation, but succinic acid as already explained is formed. This acid might, however, possibly be formed by the oxidation of the γ-hydroxybutyric acid:-- COOH·CH{2}·CH{2}·CH{2}·OH + 2O = COOH·CH{2}·CH{2}·COOH + H{2}O, although this change is on biological grounds improbable. The conversion of the group ─CH(NH{2})─ into the terminal CH{2}·OH in fusel oil, or COOH in succinic acid, may possibly be effected in several different ways, the most probable of which are the following:-- I. Direct elimination of carbon dioxide, followed by hydrolysis of the resulting amine:-- (1) R·CH(NH{2})·COOH = R·CH{2}·NH{2}+ CO{2}. (2) R·CH{2}·NH{2} + H{2}O = R·CH{2}·OH + NH{3}. The reaction (1) is actually effected by many bacteria and has been employed for the preparation of bases from amino-acids [cf. Barger, 1914, p. 7], although there is no direct evidence that it can be brought about by yeast. On the other hand reaction (2) has actually been observed with some yeasts. Thus it has been found [Ehrlich and Pistschimuka, 1912, 1] that many "wild" yeasts produce this change with great readiness in presence of sugar, glycerol or ethyl alcohol as sources of carbon and grow well in media in which amines, such as p-hydroxyphenylethylamine or iso-amylamine, form the only source of nitrogen. /Willia anomala/ (Hansen), a yeast which forms surface growths, succeeds admirably under these conditions, whereas culture yeasts are much less active in this way, although they produce a certain amount of change. It is therefore possible that this mode of decomposition plays some part in the production of fusel oil, but in the case of culture yeasts it is entirely subordinated to the mode next to be discussed. [p092] II. Oxidative removal of the ─NH{2} group with formation of an α-ketonic acid:-- (1) R·CH(NH{2})·COOH + O = R·CO·COOH + NH{3} followed by the decomposition of the ketonic acid into carbon dioxide and an aldehyde and the subsequent reduction or oxidation of the aldehyde:-- (2) R·CO·COOH = R·CHO + CO{2}. (3) (/a/) R·CHO + 2H = R·CH{2}OH. (/b/) R·CHO + O = R·COOH.