REAL SOURCE OF MOTOR POWER. 925 



only for the production of heat, but also of mechanical motion . Moreover, 

 since it is improbable that, in so delicately an organized apparatus as the 

 muscular tissue, two sorts of decomposition should occur, for the purpose of 

 liberating the same force, they believe that, as non-nitrogenous substances are 

 decomposed for that purpose, those only are decomposed. The nitrogenous sub- 

 stances of the muscle, however, simultaneously undergo waste or wear, and 

 thus yield urea. In conclusion, they show that the resemblance of the living 

 animal body to a steam-engine, is more close than is usually admitted ; the 

 muscle is an apparatus for burning its appropriate fuel, the hydrocarbons and 

 carbhydrates, in the same manner as an engine burns its proper fuel, coal or 

 coke ; in action, the muscle does not specially oxidize itself, any more than 

 the engine is burnt ; but in action, both the muscle and the engine undergo 

 wear. In use, the wear, in either case, is not much increased, but the con- 

 sumption of fuel is decidedly greater. It is possible, they remark, either that 

 non-nitrogenous substances in the muscle act as the combustibles, or that they 

 pass through the muscle in a rapid stream, their particles being immediately 

 oxidized, and then carried away. 



The general conclusions of Fick and Wislicenus are strengthened by the 

 subsequent researches of Dr. Frankland, who has also supplied more secure 

 data for estimating the heat-units produced by the oxidation of albuminoid 

 substances in the body. It was admitted by the German physiologists, that 

 these could not be equal to the heat-units evolved by the combustion of the 

 separate elements of albumen out of the body, although they allowed that 

 quantity in their calculations. By mixing a certain quantity of muscle de- 

 prived of fat, albumen, and urea, all dried at 212 F., with chlorate of potash, 

 deflagrating the compounds, and measuring the heat evolved, by its effect in 

 raising the temperature of water, Dr. Fraukland shows that 1 gramme of 

 each of these substances respectively evolves, 5103, 4998, and 2206 heat-units. 

 Now, as the muscular substance is imperfectly oxidized in the body, forming 

 urea, or some still less completely oxidized material, it can only yield the 

 above-mentioned number of heat-units, minus the number producible by the 

 quantity of the imperfectly oxidized nitrogenous substances into which it is 

 converted in the system. Albuminoid bodies, in undergoing decomposition, 

 yield about J^d their weight of urea. Hence, using the above given data, 1 

 gramme of dried muscle oxidized in the body would yield 5103- 22 / 6 , or 5103- 

 735 heat-units = 4368 heat-units, or 1848 met. kils. of mechanical power ; for 

 1 gramme of pure albumen, the results are 4263 heat-units, or 1805 met. kils. 

 of force. Applying these data to Fick and Wislicenus' experiments, it will be 

 found that, as they eliminated respectively, nitrogen equal to 37.17 grammes, 

 and 37 grammes of albuminoid substance, the available energy they pro- 

 duced would be only 68, 690 and 68,376 met. kils. ; whilst their computed work 

 was 319,274 and 368,574 met. kils. The mean ratio of the work performed, to 

 the power derivable from the oxidation in the body of the nitrogenous sub- 

 stance of muscle, was, therefore, less than they had supposed, viz., as 5 to 1. 



Again, if the method devised by Frankland, for measuring the energy de- 

 rivable from the oxidation of albuminoid substances in the body, be correct, 

 then the determinations of Haughton and Playfair are inadmissible. More- 

 over, applying the same data to the observations of Edw. Smith on prisoners 

 working on the treadwheel, to those of Haughton on men engaged at shot 

 drill, and to those of Playfair on fully employed laborers, Frankland found 

 that the work accomplished was-, in the first case, nearly 2 to 1, in the second 

 case, more than 2 to 1, and in the last case, 1.3 to 1, in proportion to the force 

 indicated by the excreted nitrogen ; and yet, in each of these cases, unlike the 

 experiments of Fick and Wislicenus on themselves, the food contained a large 

 amount of nitrogenous substances, which increased the quantity of nitrogen 

 eliminated. Fick and Wislicenus intentionally consumed a non-nitrogenous 

 diet. 



Dr. Frankland agrees with the previous conclusions, that the transforma- 

 tion of muscle tissue is almost entirely independent of the amount of work 

 performed ; that, in Man, non-nitrogenous substances must be the chief source 

 of the energy which is transformed into muscular work ; that the muscle is an 

 apparatus in which this energy is evolved, at the expense of hydro-carbona- 



