440 



NATURE 



[Sept. 8, 1881 



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 Ijoldly applied it to the phenomena of animal life, 

 and thus re-uiiited physiology with natural philosophy, from 

 which it liad been rightly, because unavoidably, severed by the 

 vitalists of an earlier period. 



Let me (irst 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 

 U'^ing 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, for as, in the higher animal^, 

 the body can only work at a constant temperature of about 100° 

 F. , heat may be so regarded. 



Having previously determined the heat and work severally 

 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 oxidation process of the body, the quantity 

 of carbon actually 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 correlation of 

 process and product hold good, so far as its truth could then be 

 tested, as regards the whole organism, Mayer proceeded to in- 

 quire into its applicability to the particular organ whose function 

 it is "to transform chemical difference into mechanical effect " — 

 namely, muscle. Although, he said, a muscle acts under tlie 

 direction of the \\\\\, it does not derive its power of acting from 

 the will any more than a steamboat derives its power of motion 

 from the helmsman. Again (and this was of more importance, 

 as being more directly opposed to the prevalent vitalism), a 

 muscle, like the steamboats use in the doing of «ork, not the 

 material of its own structure, or mechanism, but the fuel — i.e. 

 the nutriment — which it derives directly from the blood Mhich 

 flows through its capillaries. "The muscle is the instrument liy 

 which the transformation of force is accomplished, not the 

 material which is itself transformed." This principle he exem- 

 plified in several ways, showing that if the muscle of our bodies 

 worked, as was formerly supposed, at the expense of their own 

 substance, their whole material would be used up in a few 

 weeks, and that in the case of the heart, a muscle which \\orks 

 at a much greater rate than any other, it w ould be expended in 

 as many days — a result which necessarily involved the absurd 

 hypothesis 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 %\ hole 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 investigations by 

 which these previsions have been verified. Begun by Bidder 

 and Schmidt in 1851,' continued by Pettenkofer and Voit,= and 

 by the agricultural physiologists ' with reference to herbivora, 

 they are not yet by any means completed. I must content myself 

 with saying that by these experiments the first and second parts 

 of this gre.at subject — namely, the limits of ihe chemical process 

 of animal life and its relation to animal motion under different 

 conditions — have been satisfactorily worked out, but that the 

 quantitative relations of heat production are as yet only insuffi- 

 ciently 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 



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

 Leipzig, 1852. 



= Pettenkofer and Voit. Zeitschr.f. Biologic^ passim, 1S66-80. 



^ Henneberg and Stohmann, '■ Beitrage zur Begrundung einer rationellen 

 Futterung der Wiederkauer," Brnnswick and Goltingen, iSco-70. 



as certain as of any physical fact that the animal body in doing 

 work does not use its own material— that, as Mayer says, 

 the oil to his lamp of life is food ; but in addition to this we 

 know what he was unaware of, that what is used is not only not 

 the living protoplasm itself, but is a kind of material which widely 

 differs from it in chemical properties. In what may be called 

 commercial physiology — /.,-., in the literature of trade puffs — one 

 still meets with the assumption that the material basis of muscular 

 motion is nitrogenous ; but by many methods of proof it has 

 been shown that the true " Oel in der Flamme des Lebens" is 

 not proteid substance, but sugar, or sugar-producing material. 

 The discovery of this fundamental ti-utli mc owe first to Bernard 

 (1850-56), who brought to light the fact that such material plays 

 an important part in the nutrition of every living tissue ; secondly, 

 to Voit (1866), who in elaborate experiments on carnivorous 

 animals, during periods of rest and exertion, showed that, in 

 comparing those conditions, no relation whatever shows itself 

 between the quantity of proteid material (flesh) consumed, and 

 the amount of work done ; and finally to Frankland, Fick, and 

 his associate Wislicenus, as to the work-yielding value of 

 different constituents of food, and as to the actual expenditure 

 of material in man during severe exertion. The subjects of 

 experiment used by the two last-mentioned physiologists were 

 themselves ; the work done was the mountain ascent from Inter- 

 laken to the summit of the Faulhorn ; the result was to prove 

 tliat the quantity of material used was proportional to the work 

 done, and that that material was such as to yield water and 

 carbonic acid exclusively. 



The investigators to w-hom I have just referred aimed at 

 proving the correlation of process and product for the whole 

 animal organism. The other mode of inquiry proposed by 

 Mayer, the verification of his principle in respect of the work- 

 doing mechanism — that is to say, in respect of muscle taken 

 separately — has been pursued with equal perseverance during 

 the last twenty years, and with greater success ; for in experi- 

 menting on a separate organ, which has no other functions 

 excepting those Avhich are in question, it is possible to eliminate 

 uncertainties which are unavoidable w hen the conditions of the 

 problem are more complicated. Before I attempt to sketch the 

 results of these experiments, I must ask your attention for a 

 moment to the discoveries made since Mayer's epoch, concerning 

 a closely related subject, that of the Process of Respiration. 



I wish that I had time to go back to the great discovery of 

 Priestley (1776), that the essential facts in the process of respi- 

 ration 'are the giving off of fixed air, as he called it, and the 

 taking in of dephlogisticated air, and to relate to j'ou the 

 beautiful experiments by which he proved it ; and then to pass 

 on to Lavoisier (1777), who, on the other side of the Channel, 

 made independently what was substantially the same discovery a 

 little after Priestley, and added others of even greater moment. 

 According to Lavoisier, the chemical process of respiration is a 

 slow combustion which has its seat in the lungs. At the time 

 that Mayer w rote, this doctrine still maintained its ascendency, 

 although the investigations of Magnus (1S3S) had already proved 

 its fallacy. Mayer himself knew that the blood possessed the 

 property of conveying oxygen from the lungs to the capillaries, 

 and of conveying carbonic acid gas from the capillaries to the 

 Kings, w hich w as sufficient to exclude the doctrine of Lavoisier. 

 Our present knowledge of the subject was attained by two 

 methods — viz., first, the investigation of the properties of the 

 colouring matter of the blood, since called " hemoglobin," the 

 initial step in which was made by Prof. Stokes in 1862 ; and 

 secondly, the application of the mercurial air-pump as a means 

 of determining the relations of oxygen and carbonic acid gas to 

 the living blood and tissues. The last is a matter of such im- 

 portance in relation to our subject that I shall ask your special 

 attention to it. Suppose that 1 have a barometer of which the 

 tube, instead of being of the ordinary form, is expanded at the 

 top into a large bulb of one or two litres capacity, and that, by 

 means of some suitable contrivance, I am able to introduce, in 

 such a w-ay as to lose no time and to preclude the possibility of 

 contact with air, a fluid ounce of blood from the artery of a living 

 animal into the vacuous space — w-hat would happen ? Instantly 

 the quantity of blood .w'ould be converted into froth, which 

 would occupy the whole of the large bulb. The colour of the 

 froth would at first be scarlet, but would speedily change to 

 crimson. It would soon subside, and we should then have the 

 cavity which was before vacuous occupied by the blood and its 

 gases — namely, the oxygen, carbonic acid gas, and nitrogen 

 previously contained in "it. And if we had the means (which 



