PRESIDENTIAL ADDRESS — SECTION B. 55 



compounds of Mercury were useful in the treatment of syphilis, 

 although the causal organism {Treponema pallidum.) of the 

 disease had not yet been discovered. Unfortunately, however, 

 Mercury compounds could not be used in adef|uate amount 

 owing to their poisonous action on the patient, and the problem 

 became one of getting the mercury into a dye-like compound, 

 which would be selectively fixed by the organism without kill- 

 ing the patient ; in other words, to " cover " the mercury with 

 chemical groupings for which the causal organisms had a special 

 affinity, but for which the tissues of the body had not. It was 

 soon found, however, that dye-mercury compounds were unstable 

 in the body, and that the mercury was too easily set free again 

 in a form ix>isonous for the subject. The next problem was to 

 find a substitute for mercury which could be efifectively 

 " covered " in such a way as to combine a harmless grouping for 

 v/hich the disease organism had some special affinity, with a 

 toxic group which would kill it. The element arsenic seemed 

 promising, and Ehrlich, in colloboration with others, finally 

 succeeded in preparing tfie compound " Salvarsan," the chemical 

 name for which is 3 : 3'-diamino-4 : 4' — -dihydroxyarsenoben- 

 zene-dihydrochloride. Only the expert chemist can realise the 

 enormous amount of labour and ingenuity expended in the re- 

 search which culminated so brilliantly ; involving, as it did, the 

 devising of methods for synthesising unknown organic deriva- 

 tives of arsenic, and the elaborate testing of the new compounds. 

 But some idea of the labour involved is indicated by its 

 laboratory nick-name " 606 " — success came only after the six 

 hundred and sixth compound was prepared. Further researches, 

 along similar lines, for specifics against bacteria, spiroch?etes, 

 and trypanosomes. are now in progress all over the world, and 

 it seems probable that a new era has been heralded in the long 

 combat against disease. But the practitioner must not expect 

 immediate results. The number of compounds of the class 

 under consideration is rapidly going up into the thousands, but 

 the chase is a long one. One of the most recent derivatives, 

 " Margol " or " 102." is a complex organic compound of arsenic, 

 antimony, and silver, and is claimed to be superior to Salvarsan 

 for the treatment of Syphilis. As the connection between 

 chemical constitution and physiological action becomes gradually 

 worked out by the pure sciences, fresh lines of application to 

 medicine will suggest themselves. 



It would take us too far ofif the main track of the ramifica- 

 toins of chemistry to go into other subdivisions of the borderline 

 science of biochemistry. 



On the industrial side, it may be mentioned that subjects 

 such as Brewing are dominantly biochemical, and that the 

 director of the school of Brewing in the University of Birming- 

 ham is a biochemist of the first order, who has turned out work 

 of fundamental interest to the science. In Birmingham Univer- 

 sity a diploma in Brewing is granted to students taking a three- 



