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TRANSACTIONS OF THE SECTIONS. 131 



important therapeutic agents, but to a knowledge of the relation -which exists 

 between the chemical constitution of a substance find its physiological effects. 

 Already a considerable amount of work of this kind has been accomplished. The 

 physiological action of the various anajsthetics (such as chloroform, chloral, alcohol, 

 &c.), of narcotics (such as morphia, narceine, narcotine, codeine, and many others), 

 and of alkaloids (such as strychnine, brucine, nicotine, atropine, hyoscyamine, physo- 

 stigmine, muscarine, veratrine, acouitine, digitaliuc, santonine, ergotine, and quinine) 

 has been carefidly studied. The celebrated research of Professor Crum Brown 

 and Dr. Thomas K. Fraser, upon tlie physiohigical action of the methyl-, amyl-, and 

 ethyl-substitution compounds of ceitaiu aUialoid^, in which they showed that a 

 change in chemical composition was attended by a change in physiological action, 

 opened up a new held of discoveiy. The investigations of Dr. B. W. Richardson 

 on the action of homologous series of alcohols and ethers, and the obsers'ations 

 made by Professor Dewar and myself on the action of the chinoHne and pyridine 

 series of bases, and their substitution compoiuids, all tended to illustrate the same 

 general truth. Nor must I forget to mention an interesting series of investigations 

 made by Professor Gamgee, of Manchester, and his pupils, communicated to our 

 Section' and at the present meeting, on the action of Aarious compoiuids of the 

 rare metal vanadium, on the action of chromimu salts, and on the differences 

 between the physiological actions of ortho-, meta-, and pyi-o-phosphoric acids. 

 Here, again, we had a further illustration of the important facts that the physio- 

 logical action of any active substance is affected (1) by the number of atoms in the 

 molecule and its complexity of structure, and (2) by the degree of stability of the 

 molecule. Tliat is to say, the more coniplex the molecule, the more intense and 

 prolonged Avill its action probably be ; and, on the other hand, if the molecule of a 

 substance tend readily to break dovm or split up while circulating in the blood, it 

 will act more intensely than if it held firmly togetiier for a considerable time. 

 These generalizations are merely tentative. Vre have not yet sufficient data to 

 entitle us to term them general laws. 



Now no one can glance oxer any work on organic chemistry without seeing on 

 e^-ery page the names of substances regarding the physiological action of which we 

 know nothing. I would not have these mvestigated in a promiscuous manner, 

 with the vague hope of coming upon something new. Here, as elsewhere in 

 science, we must be guided so far by the light cast upon the unkno-«ai by former 

 discoveries, and by those general laws which have been formulated by previous 

 im-estigators. Nor is the mere discovery of new poisons any thing but a " sorry 

 task," unless the research lead us to an agent likely to be of therapeutic value, or 

 to the enimciation of an important general principle. But former experience 

 warrants us in hoping, nay in expecting, that new useful agents will yet be disco- 

 ■\ered. I need not refer to the practical applications of cliloroform and ether, as 

 these are too well known to need any eulogy from me ; but I may be allowed to 

 direct attention to chloral, first discovered by Liebig in 18.32, and known for many 

 years merely as the ultimate product of chlorine upon alcohol. It was only a few 

 years ago that Liebreich, of Berlin, pointed out its important physiological action, 

 and it is now recognized as a therapeutic agent of the highest Aalue. Its use, no 

 doubt, has often been sadly abused, and people have often trifled with a powerful 

 physiological agent even to the loss of their lives ; but when we think of the hours 

 of pain v\-liich many a weary sufferer has e-;caped by its use, we cannot but regard 

 it as a boon to humanity. 



Here the physiologist must go hand in hand with the chemist. The chemist in 

 his laboratory prepares the substances, and builds up new compoiuids by those 

 wonderful synthetic processes which are now the gloiy of his science ; it is then 

 the duty of the physiologist to investigate the actions of these. By imited work, 

 who can foretell what may be accomplished ? For example, may we not hope to 

 see the day when such a substance as quinine, or a substance having similar 

 therapeutic properties, may be produced artificially ; or, may we not obtain an 

 anajstnetic as potent and even less dangerous than those at present employed ? 



Nor have we yet investigated the physiological action of the active principles of 

 thousands of plants, many of which may prove to be of great value. Let us 

 remember the well-known words of Shakespeare, as Romeo — the loAe-stricken 



