The Functions of the Blood. 91 



it lias recently been demonstrated by the conjoined efforts of 

 Traube, Heidenhain, and Donders, and still more distinctly by 

 Fick and Wislicenus, Frankland and Parkes, that the oxidation 

 of nitrogenous substances cannot account for nearly all the 

 work done in the body. Traube, indeed, has started a rival 

 hypothesis, which has been accepted by Fick and Wislicenus 

 in their celebrated memoir;* namely, that the oxidation of 

 muscle contributes nothing whatever to muscular power, but 

 that the whole of the latter is derived from the oxidation of 

 non-nitrogenous bodies, such as fats and the so-called hydrates 

 of carbon. But as they agree with Liebig in placing the seat 

 of this oxidation in the tissue, there is no great difference, as 

 far as the blood is concerned, between the two views. 



But are there, indeed, two distinct kinds of oxidation 

 going on in the body, one inside and one outside the walls of 

 the blood-vessels ? Is it probable, or indeed possible, that 

 sufficient oxygen can pass out through the thin walls of the 

 capillaries to account for the enormous force exerted by the 

 body in twenty-four hours ? Mayer thought not, and argued 

 against the notion in his immortal treatise, " Organic Motion 

 in its connection with Change of Matter," published more than 

 twenty years ago.f I believe he was right in this, as in so 

 many other things, and I have elsewherej drawn attention to 

 his arguments, and endeavoured to add others to them. The 

 question is one of immense theoretical and practical impor- 

 tance, and I will therefore enter into it in some detail. 



To begin with, it is necessary to bear in mind another well- 

 known and most important function of the blood. All the 

 tissues of the body, the muscles among the number, are subject 

 to a ceaseless process of disintegration and destruction. The 

 elementary parts of which a tissue consists, have a definite 

 term of life. They are born, grow, decay, and die, having 

 previously developed new germinal matter from which their 

 successors arise. There is no doubt about this, and it is 

 equally certain that the nutrient matter, the pabulum, from 

 which the new parts are formed and nourished, is derived from 

 the blood, some portion of which must travel through the thin 

 walls of the capillaries, and irrigate the tissue. Extreme un- 

 certainty exists as to the mode in which this exudation takes 

 place. At first sight it would appear to be simply a question 

 of liquid diffusion ; but, apart from the colloidal nature of the 

 albuminous bodies of the blood, there are some striking points 

 of difference between the composition of the blood and that of 



* " On the Origin of Muscular Power," " PhU. Mag.," June, 1866 

 (Supplement). 



t "Die Organische Bewegung in ilirem Zusammenhanga mit dem Stoff- 

 wechsel." Heilbronn, 1845. 



% " Phil. Mag.," May, 1867. 



