TRANSACTIONS OF SECTION D. DEPT. ANATOMY ATJD PHYSIOLOGY. 709 



the presence of ' effete matter,' as used to be thought, but on the less amount of 

 oxygen held by its colouring matter, and that the blood which flows back to the 

 heart from different organs, and at different times, differs in the amount of oxyuen 

 and of carbonic acid gas it yields, according to the activity of the chemicarpro- 

 cesses which have their seat in the living tissues from which it flows." But this 

 is not all that the blood-pump has done for us. By applying it not merely to the 

 blood, but to the tissues, we have learnt that the doctrine of Lavoisier was wrnnc 

 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 fact constantly tearing it from the hsemoglobiu which holds it, yet they them- 

 selves 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 

 compelled 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 

 understand 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 found. Not- 

 withstanding that no oxidation-product is formed, it becomes latent in every bit of 

 living protoplasm ; stored up in quantity 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 localised 

 oxidation in the capillaries, believed it to be. And this difference has a good deal to 

 do with the relation of Process to Product in muscle. Let us now revert to the 

 experiments on this subject which we are to take as exemplification of the truth 

 of Mayer's forecasts. 



The living muscle of a frog is placed in a closed chamber, which is vacuous — 

 i.e. contains only aqueous vapour. The chamber is so arranged that the muscle 

 can be made to contract as often as necessary. At the end of a certain period it 

 is found that the chamber now contains carbonic acid gas in quantity correspond- 

 ing to the number of contractions the muscle has performed. The water which 

 it has also given off cannot of course be estimated. Where do these two products 

 come from ? The answer is plain. The muscle has been living all the time, for 

 it has been doing work, and (as we shall see immediately) producing heat. What 

 has it been living on? Evidently on stored material. If so, of what nature .P 

 If we look for the answer to the muscle, we shall find that it contains both proteid 

 and sugar-producing material, but which is expended in contraction we are not 

 informed. There is, however, a way out' of the difficulty. We have seen that 

 the only chemical products which are given off' during contraction are carbonic 

 acid gas and water. It is clear, therefore, that the material on which it feeds 

 must be something which yields, when oxidised, these products, and these only. 

 The materials which are stored in muscle are oxygen and sugar, or something 

 resembling it in chemical composition. 



And now we come to the last point I have to bring before you in connection 

 "With this part of my subject. I have assumed up to this moment that heat is 

 always produced when a muscle does work. Most people will be ready to admit 

 as evidence of this, the familiar fact that we warm ourselves by exertion. This is 

 in reality no proof at all. 



The proof is obtained when, a muscle being set to contract, it is observed that at 

 each contraction it becomes warmer. In such an experiment, if the heat-capacity of 

 muscle is known, the weight of the particular muscle, and the increase of tempera- 

 ture, we have the quantity of heat produced. 



If you determine these data in respect of a series of contractions, arranging 

 the experiments so that the work done in each contraction is measured, and 

 immediately thereupon reconverted into heat, the result gives you the total pro- 

 duct of the oxidation-process in heat. 



If you repeat the same experiment in such a way that the work done in 

 each contraction is not so reconverted, the result is less by the quantity of heat 

 Ludwig's first important research on this subject was published in 18fi2. 



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