B.— CHEMISTRY. 61 



seems pretty well established, and analogies in vitro have been found. 

 Other problems are more obscure. Why is the benzene nucleus in phenyl- 

 alanine oxidised, but not that in benzoic acid ? And what is the mechanism 

 in the former case ? Why is p-hydroxyphenyl pyruvic acid easily oxidised, 

 and the corresponding lactic acid not ? Why is d-phenylglycine easily 

 oxidised and 1-phenylglycine excreted almost unchanged ? Altogether 

 the processes by which organic substances are burnt to carbon dioxide 

 and water, by atmospheric molecular oxygen, at a low temperature, are 

 still very puzzling, although Dakin, Hopkins, Knoop, Warburg, Wieland, 

 and others have done much towards their elucidation. In the study of 

 the chemical processes, as in that of the chemical constituents of living 

 organisms, there is much scope for the application of organic chemistry, 

 and in addition, physical chemistry reqixires to be utilised. 



I have endeavoured, by the mention of the above examples, to indicate 

 the importance of organic chemistry both to descriptive and dynamic bio- 

 chemistry, and thus to physiology. This is its main field of application 

 to biological science, but there are others. There is no reason why an 

 animal or a plant should be recognised entirely by its morphological 

 characters, but systematists, not being chemists, are naturally apt to rely 

 on what they can see, rather than what they can test for. It is very 

 rarely that chemical characteristics are mentioned, although most floras 

 refer to the odour of trimethylamine in the Stinking Goosefoot {Cheno- 

 podium vulvaria) and that of sulphide oil in Sisymbrium Alliaria. With 

 micro-organisms it is different. The bacteriologist cannot always dis- 

 tinguish one bacillus from another merely by looking at it, nor even by 

 staining it. He has to grow it in a variety of sugar solutions, and see 

 whether it attacks these. In order to differentiate typhoid from para- 

 typhoid, he grows them in dulcitol solution, with neutral red, which may 

 or may not be changed owing to the production of an organic acid from 

 the sugar. In order to encourage an organism to grow, which is normally 

 swamped by other species, he may use specific disinfectants, such as 

 brilliant green and other dyes. The relation between microbiology and 

 organic chemistry is beneficial to both. The list of organic substances 

 which can be produced by micro-organisms on an industrial scale, mostly 

 from carbohydrates, is a growing one. During the world war the water 

 power of Switzerland could temporarily compete with the fermentation 

 industry in producing alcohol {via calcium carbide), but later the potato 

 reasserted its superiority. The same war period saw the industrial pro- 

 duction of glycerol by yeast, and the production of acetone and butyl 

 alcohol by bacteria, both from carbohydrates. The peculiar metabolism 

 of many micro-organisms still awaits utilisation. 



The group of plants in which chemical constituents have been most 

 widely used in classification is that of the Lichens. Lichenologists have 

 long used chemical reactions with potassium hydroxide, bleaching powder 

 and ferric chloride, for the identification of species and genera, and some 

 200 characteristic benzene derivatives have been isolated. In Phanero- 

 grams the taxonomic value of the chemical constituents is sUght. Sub- 

 stances of obvious metabolic significance may extend throughout a whole 

 order ; thus inulin occurs as reserve carbohydrate in all divisions of the 

 Compositae. 



