1867.] Food as a Motive Power. 341 



Alluding to one of Graham's recent discoveries, he said : — " The 

 importance of this discovery in metallurgy, and its application to 

 the physiology of respiration and of the passage of oxijgen from the 

 blood into the textures, must be apparent to all." But nothing 

 could be more unlikely, on chemical grounds, than such a mode of 

 oxidation. Oxygen, when just liberated from combination, is 

 usually more active in entering into new combinations,* and yet, 

 here we are called upon to believe that a great portion of it leaves 

 one combination without any assignable cause, and remains for a 

 time in a free state, although present in the same solution with 

 matters for which it has a great affinity. That the oxygen of the 

 colouring matter is capable of combining directly with some of the 

 nitrogenous compounds of the blood, is evident from an experiment 

 of Stokes's, in which a solution of blood was found to reduce itself 

 when preserved in a closed vessel. The experiment further proves 

 that the oxidizing power of the blood is not necessarily dependent 

 upon nerve-action, although it may, very probably, be stimulated by 

 it. Mayer saw this difficulty in the current theory of tissue-oxida- 

 tion, and met it by placing the seat of all oxidation in the blood, 

 and by assigning to the corpuscles the office of effecting directly the 

 whole of it. Both heat and muscular work derive their source, 

 according to him, from blood-oxidation, some portion of the oxida- 

 tion yielding work, the remainder heat. He says, " The muscle 

 produces mechanical work at the expense of the chemical action 

 expended in its capillary vessels." 



Claude Bernard seems to have adopted a similar view, and 

 expresses it occasionally with great clearness. The following pas- 

 sage occurs in his celebrated ' Lecons sur les Liquides de l'Or- 

 ganisme : ' t — 



"II est infiniment probable que l'acide carbonique du sang 

 veineux resulte d'une oxydation qui s'est effectuee dans le globule 

 sanguine lui-meme. Lorsque le sang traverse les capillaires, il y 

 aurait entre lui et les tissus non echange de gaz, mais peut-etre 

 echange de liquides. Par suite des conditions nouvelles que 

 creerait cet echange, l'oxygene du globule serait en partie employe 

 a oxyder le carbone du globule lui-meme." 



This therefore is the third, and it appears to me the only tenable 

 hypothesis of the source of muscular power. I shall speak of it as 

 Mayer's hypothesis. The blood is the seat of all oxidation, and 

 therefore the originator of all force in the body. Some part of this 

 force is evolved in the form of muscular work, the greater part of 



* It is, however, right to add, that oxygen is probahly held in craorine, in 

 what Kekule calls "molecular combination," since it has been shown that car- 

 bonic oxide displaces from it its own volume of oxygen. In this case the liberated 

 oxygen would not be more than usually active. 



t Vol. i., 342. 



