360 AN AMERICAN TEXT- BOOK OF PHYSIOLOGY. 



struction of proteid and an increase in the nitrogenous excretions. That the 

 total energy of muscular work is not derived from the oxidation or metabolism 

 of proteid alone was clearly demonstrated by the famous experiment of Fick 

 and Wislicenus. These physiologists ascended the Faulhorn to a height of 

 1956 meters. Knowing the weight of his body, each could estimate how much 

 work was done in ascending such a height. Kick's weight, for example, was 

 66 kilograms, therefore in climbing the mountain he performed 66 X 1956 = 

 129,096 kilogrammeters of work. In addition, the work of the heart and the 

 respiratory muscles, which could not be determined accurately, was estimated 

 at 30,000 kilogrammeters. There was, moreover, a certain amount of muscular 

 work performed in the movements of the arms and in walking upon level 

 ground that was omitted entirely from their calculations. For seventeen hours 

 before the ascent, during the climb of eight hours, and for six hours afterward 

 their food was entirely non-nitrogenous, so that the urea eliminated came entirely 

 from the proteid of the body. Nevertheless, when the urine was collected and 

 the urea estimated it was found that the potential energy contained in the pro- 

 teid destroyed wasentirely insufficient to account for the work done. Although 

 later estimates would modify somewhat the actual figures of their calculation, 

 the margin was so great that the experiment has been accepted as showing 

 conclusively that the total energy of muscular work does not come necessarily 

 from the oxidation of proteid alone. Later experiments made by Voit upon 

 a dog working in a tread- wheel and upon a man performing work while in the 

 respiratorv chamber (p. 344) gave the surprising result that not only may the 

 energy of muscular work be far greater than the potential energy of the proteid 

 simultaneously oxidized, but that the performance of muscular work within 

 certain limits does not affect at all the amount of proteid metabolized in the 

 body, since the output of urea is the same on working-days as during days of 

 rest. Careful experiments by an English physiologist, Parkes, made upon 

 soldiers while resting and after performing long marches showed also that 

 there is no distinct increase in the excretion of urea after muscular exercise. 

 It followed from these experiments thai Liebig's theory as to the source of 

 the energy of muscular work is incorrect, and that the increase in the oxida- 

 tions in the body that undoubtedly occurs during muscular activity must 

 affect only the non-proteid material, that is, the fats and carbohydrates. More 

 recently the question was reopened by experiments made under Pfluger 

 by Argutinsky. ' In these experiments the total nitrogen excreted was deter- 

 mined with especial care in the sweat as well as in the urine and the feces. 



The muscular work d consisted in long walks and mountain-climbs. 



Argutinsky found that work caused a marked increase in the elimination of 

 nitrogen, the increase extending over a period of three days, and he estimated 

 that the additional proteid metabolized in consequence of the work was suf- 

 ficient to account for most of the energy expended in performing the walks 

 and climbs. A number of objections have been made to Argutinsky 's work. 

 It has been asserted that during his experiment he kept himself upon a 

 ! Pfluger^ Archiv fur die gesammte Physiologie, 1890, vol. 46, p. 552. 



