TRANSACTIONS OF SECTION D. DEPT. ANATOMY ^ND PHYSIOLOGY. 707 



for as, in the higher animals, the body can only -work at a constant temperature of 

 about 100° Fahr., 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 inquire into its applicability to the particular organ 

 whose function it is ' to transform chemical difterence into mechanical effect ' — 

 namely, muscle. Although, he said, a muscle acts under the direction of the will, 

 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 im- 

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

 the steamboat, uses, 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 principle he exemplified in several ways, showing that if the 

 muscles 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 works at a much greater rate than any other, 

 it would be expended in as many days — a result which necessarily involved the 

 absurd hypothesis that the muscular fibres of our hearts are so frequently disin- 

 tegrated and reintegrated that we get new hearts once a week. 



On such considerations Mayer founded the prevision, that, as soon as experi- 

 mental methods should become sufficiently perfect to render it possible to deter- 

 mine 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 quanti- 

 tative 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 veri- 

 fied. Begun by Bidder and Schmidt in 1851,i 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" 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 quan- 

 titative 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 far it falls short of or ex- 

 ceeds them. First of all, we are 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 — i.e. 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 



' Bidder and Schmidt, IHe Verdauungssaefte und der Stoffwechsel, Leipzig, 1852. 

 ^ Pettenkofer and Voit, Zeitschr.f. Biologic, passim 1866-1880. 

 ' Henneberg and Stohmann, Beitrdge zur Begnindung einer rationellen Fxttterunff 

 der ^lederkdver, Brunswick and Gottingen, 1860-1870. 



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