706 EEPOET — 1881. 



■what does muscular action consist — that is, what is the process of which it is th& 

 efi'ect or outcome ? and (2) how are the motions of our bodies co-ordinated or 

 regulated ? It is unnecessary to occupy time in showing that, excluding those 

 higher intellectual processes which, as they leave no traceable marks behind them, 

 are beyond the reach of our methods of investigation, these two questions comprise 

 all others concerning animal motion. I will therefore proceed at once to the first 

 of them — that of the process of muscular contraction. 



The years which immediately followed the origin of the British Association 

 exceeded any earlier period of equal length in the number and importance of the 

 new facts in morphology and in physiology which were brought to light ; for it 

 was during that period that Johannes Mliller, Schwann, Henle, and, in this country, 

 Sharpey, Bowman, and Marshall Hall, accomplished their productive labours. But 

 it was introductory to a much greater epoch — the greatest, I venture to say, 

 beyond comparison, which has occurred in the history of Biology since that of the 

 discovery of the circulation of the blood. It would give you a true idea of the nature 

 of the great advance which took place about the middle of this century if I were to 

 define it as the epoch of the death of ' vitalism.' Before that time, even the greatest 

 biologists — e.ff. J. Mliller — recognised that the knowledge biologists possessed 

 both of vital and physical phenomena was insufficient to refer both to a common 

 measure. The method, therefore, was to study the processes of life in relation to each 

 other only. Since that time it has become fundamental in our science not to regard 

 any vital process as understood at all, unless it can be brought into relation with 

 physical standards, and the methodsof physiology have been based exclusively on this 

 principle. Let us inquire for a moment what causes have conduced to the change. 



The most efficient cause was the progress which had been made in physics and 

 chemistry, and particularly those investigations which led to the establishment of 

 the doctrine of the Conservation of Energy. In the application of this great 

 principle to physiology the men to whom we are indebted are, first and fore- 

 most, J. R. Mayer, of whom I shall say more immediately ; and secondly, the 

 great physiologists still living and working among us, who were tbe pupils of 

 J. Miiller — viz., Helmholtz, Ludwig, du Bois-Reymond, and Briicke. 



As regards the subject which is first to occupy our attention, that of the 

 process of muscular contraction, J. R. Mayer occupies so leading a position that 

 a large proportion of the researches whicb have been done since the new era, 

 which he had so important a share in establishing, may be rightly considered as 

 the working out of principles enunciated in his treatise ' on the relation between 

 organic motion and exchange of material. The most important of these were 

 as expressed in his own words, (1) ' That the chemical force contained in the 

 ingested food and in the inhaled oxygen is the source of the motion and heat 

 which are the two products of animal life ; and (2) that these products vary in 

 amoimt with the chemical process which produces them.' Whatever may be the 

 claims of Mayer to be regarded as a great discoverer in physics, there can be no 

 doubt that as a physiologist he deserves the highest place that we can give him, 

 for at a time when the notion of the correlation of different modes of motion was 

 as yet very unfamiliar to the physicist, he boldly applied it to the phenomena of 

 animal life, and thus re-united physiology with natural philosophy, from which it 

 had been rightly, because unavoidably, severed by the vitalists of an earlier 

 period. 



Let me first endeavour shortly to explain how Mayer himself applied the 

 principle just enunciated, and then how it has been developed experimentally 

 since his time. 



The fundamental notion is this : the animal body resembles, as regards the 

 work it does and the heat it produces, a steam engine, in which fuel is continually 

 being used on the one hand, and work is being done and heat produced on the 

 other. The using of fuel is the chemical process, which in the animal body, as in 

 the steam-engine, is a process of oxidation. Heat and work are the useful products, 



' J. R. Mayer, Die organische Bemegiing i?! ihrem Zusammenliange mit dcm 

 Stoffivechsel : Ein Beitrag zwr Natv/rhunde, Heilbronn, 1845. 



