EELATION OF FOOD TO WORK, AND 277 



tity of urea excreted in various diseases, that a certaiu minimum quan- 

 tity, equivalent to 2 grains per pound of body weight, was excreted 

 quite independently of muscular exertion, and I proved that death was 

 preceded in many chronic diseases by a fall in the urea excreted to 2 

 grains per pound. These investigations were made chiefly on patients 

 dying of advanced kidney disease, in which the excretion of albumen 

 had nearly or altogether ceased, and of patients dying of phthisis. 



Pettenkofer and Voit found that tiio excretion of urea in a dog reduced 

 from 33.3 kilograms to 29 kilograms by 10 days' fast, became 8.6 grams. 

 And, since — 



29 kilograms = 03.8 pounds. 



8.6 grams = 132.7 grains. 

 Excretion of urea = 2.08 grains per pound of body weight. 



Eanke obtained a precisely similar reaalt from observations made upon 

 himself, after long fasting, continued for several days. 



If these views be well founded, it is plain that part only of the urea 

 excreted can be regarded as due to mnt:cular exertion, for 2 grains per 

 pound (or 300 grains for a man weighing' 150 pounds) must be set aside 

 as a constant due to vital work, independLiit of muscular work altogether. 

 Hence it would follow, supposing the muscular exertion to be measured 

 by the increased excretion of urea produced by it, that the urea will not 

 increase as fast as the muscular exertion, but it ought to increase regu- 

 larly, although at a slower rate. With a view to settle this important 

 question, I devised the following observations upon myself in the month 

 of July, 18G6, which j^rove conclusively that an increase of muscular 

 exertion, amounting to fourfold, is not accompanied by any correspond- 

 ing increase in the excretion of nitrogen in the form of urea. 



I had previously ascertained by repeated experiments, extending from 

 1860 to 1865, that my excretion of urea (under ordinary conditions as to 

 exercise, which never amounted to five miles per day) ranged from — 

 465. 09 grains per day, to 

 537. 47 grains per day. 



501. 28 mean. 



This quantity of urea I regarded as my natural physiological average, 

 and it was so well established that I thought I should obtain an impor- 

 tant result by comparing it with the average found from several days of unu- 

 sual muscular exertion. I accordingly walked for five consecutive days 

 in the hilly districts of Wicklow, noting carefully the horizontal distance 

 traveled each day, and the vertical height traversed up and down. The 

 vertical heights were reduced to horizontal distances, on the assumptions 

 (which are well founded) that 20 is the proper coefficient for converting 

 one into the other, and that the work of descent is half the work of 

 ascent. 



