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SCIENCE. 



as certain as of any physical fact that the animal bddyin 

 doing work does not use its own material — that, as 

 Mayer says, the oil to his lamp of life is food ; but in ad- 

 dition to this we know what he is 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 discovery of this fundamental 

 truth we 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 Interlaken 

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

 that 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 whom I have just referred aimed 

 at proving the correlation of process and product for the 

 whole animal organism. The other mode of inquiry pro- 

 posed by Mayer, the verification of his principle in re- 

 spect of the work-doing mechanism — that is to say, in re- 

 spect of muscle taken separately- -has been pursued with 

 equal perseverance during the last twenty years, and with 

 greater success ; for in experimenting on a separate 

 organ, which has no other functions excepting those 

 which are in question, it is possible to eliminate uncer- 

 tainties which are unavoidable when 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 respiration are the giving off of fixed air, as he called 

 it, and the taking in ot dephlogisticated air, and to relate 

 to you 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. Ac- 

 cording to Lavoisier, the chemical process of respiration 

 is a slow combustion which has its seat in the lungs. 

 At the time that Mayer wrote, this doctrine still main- 

 tained its ascendency, although the investigations of 

 Magnus (1838) had already proved its fallacy. Mayer 

 himself knew that the blood possessed the ptoperty of 

 conveying oxygen from the lungs to the capillaries, and 

 of conveying carbonic acid gas from the capillaries to 

 the lungs, which was sufficient to exclude the doctrine of 

 Lavoisier. Our present knowledge of the subject was 

 attained by two methods — viz., first, the investigation ot 

 the properties of the coloring matter of the blood, since 

 called " haemoglobin," the initial step in which was 

 made by Prof. Stokes in 1862; and secondly, the appli- 

 cation of the mercurial air-pump as a means of deter- 

 mining the relations of oxygen and carbonic acid gas to 

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

 such importance in relation to our subject that I shall 

 ask your special attention to it. Suppose that I have a 



barometer of which the tube, instead of being of the or- 

 dinary 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 

 way 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— what would 

 happen ? Instantlv the quantity of blood would be con- 

 verted into froth, which would occupy the whole of the 

 large bulb. The color 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 nitro- 

 gen previously contained in it. And if we had the 

 means (which actually exist in the gas-pump) of separ- 

 ating the gaseous mixture from the liquid, and of renew- 

 ing the vacuum, we should be able to determine (1) the 

 total quantity of gases which the blood yields, and (2), 

 by analysis, the proportion of each gas. 



Now, with reference to the blood, by the application of 

 the " blood-pump," as it is called, we have learned a 

 great many facts relating to the nature of respiration, 

 particularly that the difference of venous arterial blood 

 depends not on the presence of " effete matter," as used 

 to be thought, but on the less amount of oxygen held by 

 its coloring matter, and that the blood which flows back 

 to the heart frcm different organs, and at different times, 

 differs in the amount of oxygen and of carbonic acid gas it 

 yields, according to the activity of the chemical processes 

 which have their seat in the living tissues from which it 

 flows. 1 But this is not all that the blood-pump has done 

 for us. By applying it not merely to the blood, but to 

 the tissue?, we have learned that the doctrine of 

 Lavoisier was wrong, not merely as regards the place, 

 but as regards the nature of the essential process in 

 respiration. The fundamental fact which is thus brought 

 to light is this, that although living tissues are constantly 

 and freely supplied with oxygen, and are in tact con- 

 stantly tearing it from the haemoglobin which holds it, 

 yet they themselves yield no oxygen to the vacuum. In 

 other words, the oxygen which living protoplasm seizes 

 upon with such energy that the blood which flows by it 

 is compellsd to yield it up, becomes so entirely part of 

 the living material itself that it cannot be separated even 

 by the vacuum. It is in this way only that we can un- 

 derstand the seeming paradox that the oxygen, which is 

 conveyed in abundance to every recess of our bodies by 

 the blood-stream, is nowhere to be tound. Notwithstand- 

 ing that no oxidation-product is formed, it becomes latent 

 in every bit of living protoplasm ; stored up in quant. ty 

 proportional to its potential activity — i. e., to the work, 

 internal or external, it has to do. 



Thus you see that the process of tissue respiration: — in 

 other words, the relation of living protoplasm to oxygen — 

 is very different from what Mayer, who localized oxida- 

 tion in the capillaries, believed it to be. And this differ- 

 ence has a good deal to do with the relation of Process 

 to Product in muscle. Let us now revert to the experi- 

 ments on this subject which we are to take as exemplifi- 

 cation of the truth of Mayer's forecasts. 



If I only desired to convince you that during the last 

 half-century there has been a greater accession of know- 

 ledge about the function of the living organism than 

 during the previous one, I might arrange here a small 

 heap at one end of the table the physiological works of 

 the Hunters, Spallanzani, Fontana, Thomas Young, Ben- 

 jamin Brodie, Chatles Bell, and others, and then proceed ( 

 to cover the rest of it with the records of original research on 

 physiological subjects since 1 831 . 1 should find that, even if 

 I included only genuine work, I should have to heap my 

 table up to the ceiling. But I apprehend this would not give 

 us a true answer to our question. Although, etymologically, 

 Science and Knowledge mean the same thing, their real 

 meaning is different. By science we mean, first of all, 



