Prof. Frank] and on the Origin of Muscular Power, 189 



performed ; but the deficiency becomes much greater if, as Fick 

 and Wislicenus have done, we take into consideration the fact 

 that the actual energy developed by oxidation or combustion 

 cannot be wholly transformed into mechanical work. In the best- 

 constructed steam-engine, for instance, only one-tenth of the 

 actual energy developed by the burning fuel can be obtained in 

 the form of mechanical power ; and in the case of man, Helm- 

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

 developed in the body can be made to appear as external work. 

 The experiments of Heidenhain, however, show that under fa- 

 vourable circumstances a muscle may be made to yield, in the 

 shape of mechanical work, as much as one-half of the actual 

 energy developed within it, the remainder assuming the form of 

 heat. Taking, then, this highest estimate of the proportion of 

 mechanical work capable of being got out of actual energy, it 

 becomes necessary to multiply by 2 the above numbers repre- 

 senting the ascertainable work performed, in order to express the 

 actual energy involved in the production of that work. We then 

 get the following comparison of the actual energy capable of 

 being developed by the amount of muscle consumed, with the 

 actual energy necessary for the performance of the work executed 

 in the ascent of the Faulhorn. 





Fick. 



Wislicenus. 



Actual energy capable of being pro- "1 

 duced by muscle-metamorphosis . J 



Actual energy expended in work \ 

 performed J 



metrekilogs. 

 68,690 



319,274 



metrekilogs. 

 68,376 



368,574 



Thus, taking the average of the two experiments, it is evident 

 that scarcely one-fifth of the actual energy required for the work 

 performed could be obtained from the amount of muscle consumed. 



Interpreted in the same way, previous experiments of a like 

 kind prove the same thing, though not quite so conclusively. 

 To illustrate this, I will here give a summary of three sets of ex- 

 periments, — the first, made by Dr. E. Smith upon prisoners en- 

 gaged in treadmill labour; the second, by the Rev. Dr. Haugh- 

 ton upon military prisoners engaged in shot drill; and the third, 

 adduced by Playfair, and made upon pedestrians, pile-drivers, 

 men turning a winch, and other labourers. 



Treadwheel Experiments. 

 A treadwheel is a revolving drum with steps placed at distances 

 of 8 inches, and the prisoners are required to turn the wheel 

 downwards by stepping upwards. Four prisoners, designated 



