500 Drs. A. Fick and J. Wislicenus on the 



proximately, the value of the collective amounts of actual energy 

 developed in single experiments ; at least it is possible to fix a 

 point below which it will not descend. This lowest possible 

 value is almost always considerably higher than that of the equi- 

 valent of actual energy transmuted during the experiment into 

 mechanical work. It may be casually remarked that in almost 

 all Heidenhain's experiments, the mechanical work was changed 

 back again into heat ; for in every case the muscle allowed the 

 weight it had raised to fall again, so that no mechanical work 

 was really performed, and therefore the whole actual energy 

 generated could appear only in the form of heat. It appears 

 from Heidenhain's investigations, that the relation of that 

 portion of the actual energy transmuted into work to the 

 total energy produced in the contraction of muscle, varies very 

 much according to the tension of the muscle while working. 

 But we shall not be taking too high a figure if we assume that 

 this proportion can never, under normal circumstances, be 

 greater than as J to 1. According to this we must at once 

 double the numbers found above for the total amount of work 

 permanently or temporarily performed, and should thus obtain 

 a number which would give us an approximation to the sum 

 total of actual energy (expressed in units of work) which must 

 have been supplied by the force-generating processes in the 

 muscle, in order that such work might be performed. The 

 number which ought still to be added to these figures in order 

 to represent the work which had been actually performed, and 

 the statical activity of the muscles, would certainly be consider- 

 able ; but it must be omitted from the calculation, because, as we 

 said above, we have no data from which to compute it. We 

 must therefore abide by the 319,274 metre-kilogrammes for 

 Fick, and 368,574 for Wislicenus. 



It may be thought that by making use of Helmholtz's well- 

 known conclusion, we might much more easily have calculated 

 a minimum for the total actual energy provided by the processes 

 for the generation of muscular force during the ascent. By 

 ingeniously combining the results of Smith's experiments on 

 respiration with Dulong's determinations of animal heat, and 

 with the well-established hypothesis concerning capability of 

 work in man, that physiologist inferred that in the human body 

 not more than one-fifth of the heat produced by the oxidation of 

 metamorphosed substances is transmuted into muscular work. 

 It would seem, according to this, that we might obtain the 

 minimum value which we require simply by multiplying the esti- 

 mated amount of muscular work by five. But this is not the 

 case ; for Helmholtz does not separate the processes which gene- 

 rate muscular power from the somewhat different ones which pro- 



