1867.] Zoology and Animal Physiology. 293 



is to be a sound one. It is an assumption, the truth of which 

 ought to be proven, that the rate of transmission of muscular 

 force is the same in all animals. 



The Origin of Muscular Power. — The view held by Liebig, 

 and till lately implicitly received as true, that muscular power is 

 due to muscle-oxidation, has been, during the last few months, 

 rudely shaken. Professors Fick and Wislicenus, in an ascent of 

 the Faulhorn in Switzerland, found that the amount of measured 

 work performed in the ascent exceeded by more than three-fourths 

 the amount which it would be theoretically possible to realize from 

 the maximum amount of muscle-oxidation, indicated by the total 

 quantity of nitrogen in the urine. These two observers had, 

 however, to content themselves with the theoretically possible 

 force, and hence there was an experimental gap in their reasoning. 

 This has been supplied by Professor Frankland ; he has made an 

 extensive series of experiments on the oxidation of muscle and 

 urea in oxygen, and has made a calorimetrical determination of the 

 actual energy evolved by the combustion of these bodies. His ex- 

 periments are recorded in full in a late number of the ' Philosophical 

 Magazine,' and the various steps of the very intricate process through 

 which he has successfully carried his observations fully described. 

 Since the oxidation of muscle-tissue in the body has, as one of its 

 products, urea, it is necessary to make allowance for the potential 

 energy of this urea in applying the results of the complete oxida- 

 tion of muscular tissue to the question at issue. It is also neces- 

 sary to make allowance for the fact that all the energy developed 

 in the body cannot be made to appear as external work. Helmholtz 

 estimates that not more than one-fifth of the actual energy de- 

 veloped can be made to appear as external work ; while Heidenhain, 

 under favourable circumstances, allows one-half. Taking this last 

 estimate, Dr. Frankland finds that only one-fifth of the work done 

 by the two professors could be accounted for by the oxidation of 

 their muscular tissue, as indicated by the urine. He further reviews 

 the results of Dr. E. Smith's, Dr. Haughton's, and Dr. Playfair's 

 experiments, applying his determination of the " mechanical equi-' 

 valent " of muscle-oxidation to their results. 



The work done in the body is then evidently due merely to 

 the oxidation of the food held in the blood. The chief use of nitro- 

 genous food is to build up muscle-tissue, which, like the cylinder 

 and piston of the steam-engine, does not contribute to the work 

 performed by its oxidation, but is the means of converting chemical 

 and thermal modes of force into motion ; the force being really ob- 

 tained by the oxidation of principally carbonaceous, but to some 

 extent also nitrogenous, foods contained in the blood. 



The Value of Nitrogenous and Carbonaceous Foods. — This 

 question, which is one obviously resulting from the conclusions ar- 



