732 THE POPULAR SCIENCE MONTHLY. 



eight and one-fifth miles, the average proportionate excretion of 

 nitrogen by the kidneys was 86.58 parts for every 100 parts of nitrogen 

 of food. 



For the five days of the walk, the average daily exercise being 

 sixty-three and one-half miles, the average proportionate excretion of 

 nitrogen by the kidneys was 143.98 parts for every 100 parts of nitro- 

 gen of food. 



For the five days after the walk, the average daily exercise being 

 two and one-fifth miles, the average proportionate excretion of nitro- 

 gen by the kidneys was 77.03 parts for every 100 parts of nitrogen 

 of food. 



These facts showed conclusively that, in this instance, at least, the 

 extraordinary exertion of walking three hundred and seventeen and 

 one-half miles in five consecutive days very largely increased the pro- 

 portionate excretion of nitrogen by the kidneys. 



The source of the excess of nitrogen excreted during the walk must 

 have been the excessive wear of muscular tissue engendered by the 

 extraordinary exertion, which was not repaired by the food. This is 

 rendered almost certain by the following calculation : 



At the beginning of the walk, Weston was in good condition, with 

 little or no fat, and he weighed 119.20 pounds. "At the end of the 

 five days' walk, the weight had been reduced from 119.20 to 115.75 

 pounds, showing a loss of 3.45 pounds. According to Payen, three 

 parts of nitrogen represent one hundred parts of fresh muscular tissue. 

 The total quantity of nitrogen discharged during these five days was 

 1,811.62 grains. The total nitrogen of food during the same period 

 amounted to 1,173.82 grains, giving an excess of 637.80 grains of nitro- 

 gen discharged over the nitrogen of food. The 637.80 grains of nitro- 

 gen, according to Payen's formula, would represent 21,260.00 grains, 

 or 3.037 pounds of muscular tissue. The actual loss of muscular tis- 

 sue was 3.45 pounds, and the loss unaccounted for, amounting to only 

 0.413 of a pound, is very small. It might be fat or water, or the dif- 

 ference might be due to inaccuracies in the estimates of the nitrogen 

 of food, which, of necessity, were approximative." 



In 1876, Dr. Pavy, of London, made a series of experiments upon 

 Perkins, a pedestrian, and upon Weston, similar to those made by 

 Prof. Flint upon Weston, in 1870. The following were the general 

 results of these observations : 



Perkins walked sixty-five and one-half miles in twenty-four hours. 

 During this time, he excreted 190.37 parts of nitrogen by the kidneys 

 for every 100 parts of nitrogen of food. For twenty-four hours of rest, 

 several days after this walk, Perkins excreted 76.58 parts of nitrogen 

 by the kidneys for every 100 parts of nitrogen of food. 



Observations were made upon Weston for eleven days of walking, 

 as follows : 1. A walk of one hundred and eighty and one-half miles 

 in two consecutive days; 2. A walk of two hundred and sixty-three 



