708 . BEPORT — 1881. 



discovery of this fundamental truth we owe first to Bernard (1850-56), who l)rouglit 

 to lio-ht 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 com- 

 paring 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 

 chat material was such as to yield water and carbonic acid exclusively. 



The investigators to whom I have just referred aimed at proving the correla- 

 tion 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 experimenting on a separate organ, which has no other functions 

 excepting those which are in question, it is possible to eliminate uncertainties 

 which are unavoidable when the conditions of the problem are more complicated. 

 Before I attempt to sketch the results of these experiments, 1 must ask your atten- 

 tion 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 of 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 ascendancy, although the investigations of Magnus (1838) had already 

 proved its fallacy. Mayer himself knew that the blood possessed the property of con- 

 veying 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 of the properties of the colouring matter of the blood, 

 since called ' haemoglobin,' the initial step in which was made by Professor 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 importance 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 way as to lose no time and to preclude the possi- 

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

 into the vacuous space — what would happen ? Instantly the quantity of blood 

 would 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 

 actually exist in the gas-pump) of separating the gaseous mixture from the liquid, 

 and of renewing 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 learnt a great many facts relating to the nature of respira- 

 tion, particularly that the difference of venous from arterial blood depends not on 



