TRANSACTIONS OF SECTION D. 605 



of the subject, and the nature of the work which the physiologist has to do. 

 That work is of two kinds. He has first to determine what are the chemical and 

 physical endowments of living matter in general, and of each of the varieties of 

 living matter which constitute the animal and plant organism in particular. 

 Then, these having been investigated, he has to determine how these processes are 

 localised so as to constitute the special function of each structure, and the relation 

 between structure and process in each case. The order I have indicated is the 

 logical order, but in the actual progress of physiology this order has not been 

 followed, i.e. there has not been a correlation of structure with previously inves- 

 tigated process, for in former days physiologists spoke of assimilation, secretion, 

 contraction and the like, as functions of muscU^s, glands, or other parts, without re- 

 cognising their ignorance of their real nature. But now, no one who is awake to the 

 tendencies of thought and work in physiology, can fail to have observed that the 

 best minds are directed with more concentration than ever before to those questions 

 which relate to the elementary endowments of living matter, and that if they are 

 still held in the background it is rather because of the extreme difficulty of 

 approaching them than from any want of appreciation of their importance. 



It is to some of these questions that I am anxious to draw the; attention of the 

 Section to-day. I feel that I have set myself a difficult task, but think that, even 

 should I succeed very partially, the attempt may be a useful one. And I am 

 encouraged by the consideration that the interest they possess is one which is 

 common to plant and animal physiology, and that if we really understood them, 

 they woidd furnisli a key, not only to the phenomena of nutrition and growth, 

 but even to those of reproduction and development, and by the belief that it is in 

 the direction of elementary physiology, which means nothing more than the study 

 of the endowments of living material, that the advance of the next twenty years 

 will be made. 



Nearly fifty years ago, J. R. Mayer's * treatise on the relation between organic 

 motion and the exchange of material in living organisms was published in 

 Germany. Although its value was more appreciated by physicists than by 

 biologists, it was in its purpose, as well as in its subject-matter, physiological. In 

 it Mayer showed for the first time that certain functions of the animal body, which 

 up to that time had been considered most vital, are strictly within reach of 

 measurement, i.e. referable to physical standards of quantity. He was even able 

 to demonstrate that those quantitative relations between different kinds of energy 

 which physicists were then only beginning to recognise, held good as regards the 

 processes peculiar to the living organism. 



Almost immediately after the appearance of this now celebrated work, a series 

 of discoveries were made in physiology, which constituted the period we are now 

 considering an epoch. Mayer himself had proved that muscles in doing work and 

 producing heat do not do so at the expense of their own substance. But this fact 

 could not be understood until Bernard showed that sugar is one of the most 

 important constituents of the blood, and its storage and production a chief function 

 of the liver. Helmholtz next succeeded in proving what Johannes Muller - had 

 declared to be nearly impossible, namely, that the time occupied by the propagation of 

 a motor impulse from the brain to a muscle could be measured, and showed it to be 

 proportional to the distance traversed. Next, du Bois-Reymond investigated the 

 electrical phenomena of living beings, and marshalled them under a physical 

 theory which stood its ground against the severest criticism for more than a 

 generation. And finally the hydrodynamic principles relating to the circulation, set 

 forth by Dr. Thomas Young in his Croonian Lecture forty years before, were 

 demonstrated experimentally by Ludwig, at the very time when Helmholtz 

 was giving definite form to the great natural philosopher's Theory of Colour 

 Perceptions. 



The effect of these discoveries was to produce a complete revolution in the 



' J. R. Mayer, Bie organische Bewegung in ihrem Zusammenliange mit dem Stoff- 

 n«chtel. Heilbronn. 1845. 



' Mviller's Physiology. Translation of 2nd edition, p. 729. 



