SCIENCE. 



487 



which it is the effect 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 physiology which were brought 

 to light ; for it was during that period that Johannes 

 Miiller, Schwann, Henle, and, in this country, Sharpey, 

 Bowman, and Marshall Hall, accomplished their produc- 

 tive labors. But it was introductory to a much greater 

 epoch. 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 

 biologist — e.g. J. Miiller — recognized that the knowledge 

 they possessed, both of vital and physical phenomena, 

 was insufficient to refer both to a common measure. The 

 method, therefore, was to study the process of life in 

 relation to each other only. Since that time it has be- 

 come 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 methods of 

 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 applica- 

 tion of this great principle to physiology, the men to 

 whom we are 'indebted are, first and foremost, J. R. 

 Mayer, of whom I shall say more immediately ; and 

 secondly to the great physiologists still living and working 

 among us, who weie the pupils of J. Miiller — viz.; Helm- 

 holtz, Ludwig, Du Bois-Reymond, and Briicke. 



As regards the subject which is first to occupy our atten- 

 tion, that of the process of muscular contraction, J. R. 

 Mayer occupies so leading a position that a large propor- 

 tion of the researches which 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 1 on the relation between or- 

 ganic motion and exchange of material. The most im- 

 portant 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 amount with the chemical 

 process which produces them." Whatever may b^ the 

 claims of Mayer to be regarded as a great discovery 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 endeavor 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 re- 

 sembles, as regards the work it does and the heat it pro- 

 duces, a steam-engine in which fuel is continually being 

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



1 J. K. Mayer, " Die organische Bewegung in ihrem Zusammen- 

 hange mit dem Stoffwechsel ; ein Beitrag zur Naturkunde,' Heilbronn, 

 1845- 



produced on the other. The using of fuel is the chemical 

 process, which in the animal body, as in the steam en- 

 gine, is a process of oxidation. Heat and work are the 

 useful products, for as, in the higher animals, the body 

 can only work at a constant temperature of about ioo° 

 F., heat may be so regarded. 



Having previously determined the heat and work sev- 

 erally producible by the combustion of a given weight of 

 carbon, from his own experiments and from those of 

 earlier physicists, Mayer calculated that if the oxidation 

 of carbon is assumed to represent approximately the oxi- 

 dation process of the body, the quantity of carbon actu- 

 ally burnt in a day is far more than sufficient to account 

 for the day's work, and that of the material expended in 

 the body not more than one-fifth was used in the doing 

 of work, the remaining four-fifths being partly used, 

 partly wasted in heat production. 



Having thus shown that the principles of the cor- 

 relation of process and product hold good, so far as 

 its truth could then be tested, as regards the whole 

 organism, Mayer proceeded to inquire into its applicabi- 

 lity to the particular organ whose function it is " to trans- 

 form chemical difference into mechanical effect " — name- 

 ly muscle. Although, he said, a muscles acts under the 

 direction of the will, it does not derive its power of act- 

 ing from the will, any more than a steamboat derives its 

 power of motion from the helmsman. Again (and this 

 was of mere importance, as being more directly opposed 

 to the prevalent vitalism), a muscle, like the steamboats 

 use in the doing of work, not the material of its own 

 structure, or mechanism, but the fuel — i. e. the nutriment 

 — which it derives directly from the blood which flows 

 through its capillaries. "The muscle is the instrument 

 by which the transformation of force is accomplished, 

 not the material which is itself transformed." This prin- 

 ciple he exemplified in several ways, showing that it the 

 muscles of our bodies worked, as was formerly supposed, 

 at the expense of their own substance, their whole mater- 

 ial would be used up in a few weeks, and that in the case 

 of the heart, a muscle which works at a much greater 

 rate than any other, it would be expended in as many 

 days — a result which necessarily involved the absurd hy- 

 pothesis that the muscular fibres of our hearts are so 

 frequently disintegrated and reintegrated that we get new 

 hearts once a week. 



On such considerations Mayer founded the prevision, 

 that, as soon as experimental methods should become 

 sufficiently perfect to render it possible to determine with 

 precision the limits of the chemical process, either in the 

 whole animal body or in a single muscle, during a given 

 period, and to measure the production of heat and the 

 work done during the same period, the result would show 

 a quantitative correlation between them. 



If the time at our disposal permitted, I should like to 

 give a short account of the succession of laborious in- 

 vestigations by which these previsions have been verified. 

 Begun by Bidder and Schmidt in 1851, 1 continued by 

 Pettenkoferand Voit, 2 and by the agricultural physiol- 

 ogists 3 with reference to herbivora, they are not by any 

 means completed. I must content myself with saying 

 that by these experiments the first and second parts of 

 this great subject — namely, the limits of the chemical 

 process of animal life and its relation to animal motion 

 under different conditions — -have been satisfactorily 

 worked out, but that the quantita'ive relations of heat 

 production are as yet only insufficiently determined. 



Let me sum up in as few words as possible 

 how far what we have now learnt by experiment 

 justifies Mayer's anticipations, and how it falls 

 short of or exceeds them. First of all, we are 



1 Bidder and Schmidt, " Die Verdauungssafte und der Stoffwechsel," 

 Leipzig, 1852. 



2 Pettenkofer and Voit, Zeitschr. f. Biologif. passim, 1866-80. 



3 Henneberg and Stohmann, " Beitriige zur Begiu ndung einer ratioc- 

 ellen Futterung der Wiederkauer," Brunswick and Gbttingen, 18(0-70. 



