Origin of Muscular Power. 497 



first place we may add to the data already obtained of 129,096 

 and 148,656 metre-kilogrammes another item which can be 

 expressed in units of work; and though its value cannot be 

 quite accurately calculated, yet a tolerable approximation can 

 be made. It consists of the force consumed in respiration and 

 the heart's action. The work performed by the heart has been 

 estimated, in a healthy full-grown man, at about 0-64 metre- 

 kilogramme* for each systole. During the ascent, Fields pulse 

 was about 120 per minute. That gives for the 5*5 hours of the 

 ascent an amount of work which may be estimated at 25,344 

 metre-kilogrammes, entirely employed in the maintenance of 

 the circulation. No attempt has yet been made to estimate the 

 labour of respiration. One of us has shown, however, in the 

 second edition of his ' Medical Physics' (p. 206), that Don- 

 der's well-known investigations concerning the conditions of 

 pressure in the cavity of the thorax give sufficient data for such 

 an estimate. He has there shown that the amount of work 

 performed in an inspiration of 600 cubic centims. may be rated 

 at about 0*63 metre-kilogramme. Fick breathed during the 

 ascent at an average rate of about 25 respirations per minute, 

 which gives, according to this estimation, an amount of respi- 

 ratory work for the whole ascent of 5197 metre-kilogrammes. 

 If we add this, and the number representing the work of the 

 heart, to the external work performed by Fick, we obtain a 

 total of 159,637 metre-kilogrammes, which is already half as 

 much again as the amount of heat to be obtained by the burning 

 of the albumen. In the case of Wislicenus, the relative amounts 

 are still more striking. If we suppose that his respiratory and 

 circulatory work bore the same proportion to Fick's as his bodily 

 weight did to Fick's, i. e. 7:6, we obtain for Wislicenus's 

 amount of work, as far as it is possible to calculate it, a total of 

 184,287 metre-kilogrammes, which exceeds that calculated from 

 the oxidation of the proteine substances by more than three- 

 fourths. 



Besides these estimated (and certainly not over-estimated) 

 items, there are several others which cannot be even approxi- 

 mately calculated, but the sum of which, if it could be obtained, 

 would probably exceed even our present large total. We will try 

 to give at least some sort of an account of them. It must first be 

 remembered that in the steepest mountain path there are occa- 

 sional level portions, or even descents. In traversing such places 

 the muscles of the leg are exerted as they are in ascending, but 

 the whole work performed is transformed back into heat. The 

 same force-producing process, however, must be going on in the 



* 0'43 is here assigned as the work of the left, and 0*21 as that of the 

 right ventricle. 



