“The cutaneous excretion of nitrogenous material”

Abstract

A number of experiments were reported in which the subjects wore previously extracted underclothing and at the end of the experiment the nitrogenous materials were extracted with water and determined by the Kjeldahl process. Rest and work experiments were made. During rest there is considerable variation in the actual quantity of excreted nitrogen, the average of 5 experiments being 0.071 gm. per day. The exact nature of the nitrogenous material thus excreted was not studied. A number of experiments were made on a professional bicycler, riding a bicycle ergometer. The exercise was very severe, as the total output of heat was 600 calories per hour. The bath water and the extract water from the clothing gave a total of 0.87 gm. in a 4-hour experiment, or 0.22 gm. of nitrogen per hour.

Of greatest significance is the important bearing of this channel for the excretion of nitrogenous material in experiments on the metabolism of protein. Profuse perspiration, whether induced passively or by muscular work, results in a considerable excretion of nitrogenous material through the skin. While the work engaged in by the subjects of these experiments was severe, certainly that of some of them was not extraordinarily so, and might well be equaled by many men engaged in ordinary occupations involving muscular work. A total excretion equivalent to one or more grams of nitrogen per day is not at all inconsiderable, and hence in accurate metabolism experiments we must give recognition to the possibility of excretion through this hitherto almost unconsidered channel. Especially is this so in experiments where the total amounts of nitrogen in the ingesta and egesta are smaller than normal, since the percentage error is thereby proportionally larger.