456 THE HUMAN BODY. 



foot-pounds), and Wislecenus 1805.7 X 37 = 66,810 kilo- 

 grammeters. If to the muscular work done in actually rais- 

 ing their bodies, we add that done simultaneously by the 

 heart and the respiratory muscles, and in such movements 

 of the limbs as were not actually concerned in lifting the 

 Aveight, we should have, at least, to double the above total 

 muscular work done ; and the amount of energy liberated 

 meanwhile by proteid oxidation, becomes utterly inadequate 

 for its execution. ^ It is thus clear that muscular work is not 

 wholly done at the expense of the oxidation of muscle pro- 

 teid; and it is very probable that none is so done under ordi- 

 nary circumstances, for the urea excretion during rest is 

 about as great as that during work, if the diet remain the 

 same :\f the work be very severe, as in long-distance walking- 

 matches, the urea quantity is sometimes temporarily raised, 

 but this increase, which no doubt represents an abnormal 

 wear and tear of muscle-fibre, is probably independent of the 

 liberation of energy in the form in which a muscle can use it, 

 more likely taking the form of heat ; and is, moreover, com- 

 pensated for afterwards by a diminished urea excretion. 

 Thus, hourly, before the ascent Fick and Wislecenus each 

 excreted on the average about 4 grams (62 grains) of urea ; 

 during the ascent between 7 and 8 grams (108-124 grains) ; 

 but during the subsequent 16 hours, when any urea formed 

 in the work would certainly have reached the urine, only an 

 average of about 3 grams (46.5 grains) per hour. 



It may still be objected, however, that a good deal of the 

 muscle work may be done by the energy of oxidized muscle 

 proteid ; that the amount of this oxidation occurring in a 

 muscle during rest or ordinary work is pretty constant and 

 simply takes different forms in the two cases, much as a 

 steam-engine with its furnace in full blast will burn as much 

 coal when resting as when working, but in the former case 

 lose all the generated energy in the form of heat, and in the 

 latter partly as mechanical work. Thus the smallness of in- 

 crease in urea excretion as a consequence of muscular activity 

 could be explained, while still a good deal of utilizable energy 

 might come from proteid degradation. But if this were so, 

 then the working Body should eliminate no more carbon 

 dioxide than the resting; the amount of chemical changes in 

 its muscles being by hypothesis the same, the carbon dioxide 

 eliminated should not be increased. Experiment, however, 



