338 Food as a Motive Power. [July, 



been foreshadowed by that wonderful genius Dr. Mayow, of Bath, 

 nearly 200 years ago, now began to revive, and Traube went so far 

 as to argue that the oxidation of muscle, far from being the sole cause 

 of muscular work, contributed nothing whatever to it, but that the 

 whole of the work was .done by the combustion of fats and hydrates 

 of carbon (sugar, starch, &c). Traube's calculations have been 

 shown by Professor Donders, of Utrecht, to be inconclusive, but 

 the same view has been recently maintained by two Swiss savants, 

 Fick and Wislicenus, who endeavoured to establish it by a very 

 remarkable experiment.* After abstaining for some hours from all 

 food containing nitrogen, they weighed themselves with their 

 accoutrements, and set out at day-break to ascend a neighbouring 

 mountain, the Faulhorn. They ascertained the quantity of nitrogen 

 excreted during and directly after the ascent, and calculated from it 

 the amount of muscle, or other substance of similar composition, 

 which must have been decomposed in the body to yield it. This 

 was easy enough, for nitrogen constitutes about 15 per cent, of each 

 of these substances. After applying certain necessary corrections, 

 they found that the nitrogen indicated about 37 grammes of the 

 dry muscle of each observer. They then proceeded to calculate 

 the amount of force which could be produced by the oxidation of 

 this quantity of muscle. Frankland has since determined this 

 experimentally in the same manner as he did the force-value of 

 food, and I therefore give his figures as being more reliable. He 

 finds that it is 68,376 metre-kilogrammes ; more than this amount 

 of work could not possibly have been effected by the burning in the 

 body of 37 grammes of muscle. What then was the actual work 

 accomplished by the two experimenters ? The mountain was 1,956 

 metres high. Fick weighed 66 kilogrammes and Wislicenus 76 

 kilogrammes, and these weights were raised to the top of the 

 mountain. The work which each experimenter accomplished is 

 therefore found by multiplying his weight by the height of the 

 mountain. It is equal for : — 



Fick, to 129,096 metre-kilogrammes. 



Wislicenus, to 148,656 „ 



The oxidation of muscle therefore will not account for one-half 

 of the actual work done, and if allowance be made for the work done 

 by the heart and lungs, and for the fact demonstrated by Haiden- 

 hain, that the force developed is always at least double of that actually 

 employed, the result of the experiment is even more striking. 



One part of Liebig'stheory, that, namely, which derives muscular 

 work exclusively from muscular oxidation, must therefore be finally 

 abandoned. This experiment has but supplied the finishing blow to 



* ' Philosophical Magazine,' June, 1866 (Supplement). 



