Page:Popular Science Monthly Volume 12.djvu/752

732 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 nitrogen of food.

For the five days after the walk, the average daily exercise being two and one-fifth miles, the average proportionate excretion of nitrogen 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 proportionate 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 nitrogen discharged over the nitrogen of food. The 637.80 grains of nitrogen, according to Payen's formula, would represent 21,260.00 grains, or 3.037 pounds of muscular tissue. The actual loss of muscular tissue 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 difference 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