58 SECTIONAL ADDRESSES. 



certainly a fairly simple substance, susceptible to attack by the methods 

 of organic chemistry, most progress towards isolation has been achieved 

 by selective adsorption and elution, the methods employed by Willstatter 

 for enzymes. The discovery by Eosenheim and Windaus that vitamin 

 D is formed by the irradiation of ergosterol has suddenly brought into 

 prominence a substance which before was but a curiosity, chiefly known 

 through the work of the French pharmacist, Tanret. At the same time 

 the interest of biochemists in photochemistry has been stimulated, as 

 well as in the extensive work of Windaus on the structure of cholesterol, 

 which the latter had already shown to be connected with the bile acids, 

 largely investigated by Wieland. 



The sudden emergence of ergosterol into prominence does not stand 

 alone ; another of Tanret's ergot substances, ergothioneine, at first also 

 an isolated curiosity, has acquired more general significance because it 

 has been found in mammalian red corpuscles ; it is likely that this will 

 ultimately lead to the discovery in proteins of yet another sulphur- 

 containing amino-acid, possibly a thiol histidine. Altogether ergot has 

 yielded more substances of general biological interest than any other 

 single plant. 



The above examples of the relation between biological and organic 

 chemical work relate to that division of biochemistry which may be 

 termed descriptive. A knowledge of structure is 'also necessary in 

 djmamic biochemistry, the study of the transformations which substances 

 undergo in the living organism. The recognition of the fats as esters, 

 and their behaviour to fat-splitting enzymes, the transformation of starch 

 into sugar under the influence of diastase, the end-products of alcoholic 

 fermentation, all these were early discoveries in dynamic biochemistry. 

 But just as the organic chemist may wish to know the mechanism of a 

 reaction, for instance of the Skraup synthesis of quinoline, so the bio^ 

 chemist wishes to know the intermediate steps in the transformation of 

 say glucose into alcohol. The detection of these stages of metabolism 

 is a matter of considerable difficulty, since under normal conditions the 

 intermediate substances generally disappear as rapidly as they are formed. 

 They have to be trapped by suitable means, as did Neuberg with acetalde- 

 hyde in alcoholic fermentation, or the metabolic process may sometimes 

 be cut short, by using an isolated organ, such as the surviving liver, or 

 the precursor of the intermediate substance may be administered in large 

 excess. Very little has been learned in this respect from the higher plants. 

 The very process of photosynthesis is still beset with obscurity in spite 

 of a plausible hypothesis ; we know next to nothing about transforma- 

 tion of carbohydrate into fats, and vice versa, and in particular we are 

 ignorant of the stages by which amino-acids are formed in plants from 

 nitrates and carbohydrates ; we simply do not know how the proteins of 

 living beings originate. Nor have the higher plants given us much in- 

 formation of the way in which their fats, carbohydrates, and proteins are 

 ultimately broken down. Our knowledge of catabolism is principally 

 derived from the animal world. It is found that the breakdown does 

 not always occur in the manner in which the organic chemist would expect. 

 Thus an organic chemist presented with the problem of transforming 

 stearic acid into palmitic might brominate in the alpha position, and 



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