54 PRESIDENTIAL ADDRESS — SECTION B. 



i? under way. On the botanical side it is rapidly developing 

 the independent off-shoot " Phytochemistry." The various 

 branches of agricultural chemistry, except in so far as they are 

 purely analytical, also come under the biochemical group, and 

 require a working knowledge of one or more of the biological 

 sciences. 



The science of Bacteriology, founded on a scientific basis 

 by the famous French chemist Pasteur, is an off-shoot of 

 chemistry which has long since attained its independent status, 

 and although still little more than a fusion product of Chemistry 

 and Botany in so far as pure Bacteriology, Agricultural Bac- 

 teriology, and Industrial Bacteriology, are concerned, its impor- 

 tance in human medicine has tended to associate it in the popular 

 mind with Pathology. The general medical bacteriologist, how- 

 ever, is rarely a chemist, and since the days of Pasteur pure 

 Bacteriology has suffered much from too close an association 

 with Pathology. The modern Universities are now separating the 

 two subjects. 



A new borderline between Chemistry and Pathology is fast 

 attaining importance, and progressive institutions, such as St. 

 Thomas's Hospital in London, have independent lecturers on 

 Chemical Pathology. 



Where the chemist takes to Medicine we get fresh border- 

 lines developed ; as in the case of Ehrlich, who w^as chemist 

 first and medico afterwards, and did so much for the develop- 

 ment of immuno-chemistry. It is interesting to note that the 

 famous " side-chain " theory of immunity is a direct analogy 

 from organic chemistry, and that although it has well served its 

 day the future development of immuno-chemistry promises to 

 turn on the chemistry of colloids. 



It may be added that Professor Ehrlich was also the pioneer 

 in the new line of " chemotherapy,'' a borderline between 

 chemistry and therapeutics. Since this is of popular as well as 

 of purely scientific interest, an illustration may be taken of the 

 idtimate fashion in which the discovery of new remedies in 

 medicine depends upon combination of chemcial and physio- 

 logical knowledge. " Salvarsan," " 606,'' the notoriety of 

 which has spread to the populace on account - of i,ts 

 use in curing the social scourge of syphilis, offers one 

 of the best examples. The problem before Ehrlich. when 

 he embarked upon his researches, was to obtain a poison 

 which, when injected into the blood-stream, would destroy 

 disease-producing organisms without affecting the tissues of 

 the body, i.e., to prepare a selective drug. At first sight such 

 a problem appears to be too complicated for solution, but the 

 analogy of the dyeing vat came to the rescue. It was well known 

 that certain dyes which would give a "fast colour" with silk 

 would not do so with cotton, and the same principle applied to 

 the selective staining- of bacteria and tissues, was already giving 

 fruitful results in biology. It was also empirically known that 



