Page:Thruston speech upon the progress of medicine 1869.djvu/16

 the operation of many classes of medicines upon chemical and mechanical principles.

Still more recently Dr A. C. Brown and Dr T. R. Fraser in a remarkable paper, published in the Journal of Anatomy and Physiology, have pointed out the connection between chemical constitution and physiological action, especially referring to the action of the salts of the ammonium bases derived from strychnia, brucia, thebaia, codeia, morphia, and nicotia; and Dr W. H. Broadbent has attempted to explain their results, upon the theory of varying "chemical tension" of these bodies and their relation to the chemical tension of the different parts of the nervous system. We may probably look for good fruit from such labours.

Physics have accomplished for medicine almost as much as pure chemistry. Time would not suffice even for a list of its contributions. I must therefore pass over without notice the services which have been rendered by the thermometer, by the use of heat and cold as medicinal agents, and the employment of electricity and galvanism, both in physiological experiments and in medicine. I shall turn at once to the mention of pure molecular physics, which has recently made so great progress, and which is destined to play an important part in the explanation of physiological problems.

The so-called physical forces, heat, light and electricity,