ARTICLES 423 



Van Hoft, the investigations of Bourquelot and his collaborators, 

 Bridel and Aubrey, have been the most fruitful. Bourquelot 

 was able (1911-13) to prepare a set of /S-glucosides from the 

 corresponding primary alcohols with the aid of emulsin ; and in 

 191 3 Bayliss confirmed most of this work. Later Bourquelot 

 and Bridel synthetised a-glucosides from the primary alcohols 

 with the aid of maltase of yeast. In 1916 Bourquelot and 

 Aubrey showed that a galactobiose could be synthetised by the 

 prolonged action of emulsin in a saturated solution of galactose. 

 The biose was subsequently purified by boiling the emulsin 

 and fermenting off the uncondensed galactose by yeast in the 

 presence of glucose. In 191 7 the same investigators synthe- 

 tised galactose and found that the sugar so prepared had the usual 

 reducing power and was optically active. Bourquelot and 

 Bridel (191 9) showed in the synthesis by emulsin that the pro- 

 ducts formed depend on the relative amounts of the substances 

 used. They found that the emulsin of almonds tends to form 

 only ^-glucosides when the alcohol is in excess, while if the 

 glucose is in excess the tendency is rather to the formation of 

 polysaccharides. 



The work cited in the foregoing remarks would almost lead 

 one to presume that enzymes which hydrolyse also synthetise. 

 No mention need be made of any investigations other than 

 those of Bayliss (191 3) and Krieble (1915) : they were unable 

 to confirm the results of the earlier observer, Rosenthal, who 

 claimed to have discovered an enzyme which would hydrolyse 

 but would not synthetise. 



Oxidation. — A great deal of our present knowledge of the 

 processes concerned in oxidation is based on the work of Bach, 

 who in his researches in conjunction with Chodat was the first 

 to rescue the subject from confusion. Bach's conclusions have 

 been generally accepted, but the importance of the subject has 

 become increasingly recognised, and the realisation that in it 

 may lie the key to many of the problems — pathological as well 

 as physiological — in the nutrition of animals and plants has 

 induced many observers to take up this subject within recent 

 years. 



Oxidase. — ^The subsequent work of Bach, published in several 

 papers in 191 3, is of special importance. It is presumed that 

 an organic peroxide is formed by some auto-oxidisable substance 

 in the cells of the tissues, and that oxidation takes place 

 through the freeing of active oxygen by the enzyme peroxidase, 

 which was discovered by Bach in his earlier work. In 1914 

 Bach gave support to his previous observations by showing 

 the part played by hydrogen peroxide in the reaction. He 

 observed that fresh potato juice rapidly oxidised tyrosine, but 

 that it lost this property if a certain substance or substances be 



