APPENDIX. IN discussing the various observations that have been made upon the human subject with regard to the influence of muscular exercise upon the excretion of nitrogen, I have confined myself to the question of the relations between nitrogenized food and muscular power because, in all such observations, no account has been taken of the elimination of carbonic acid. In my experiments, made in 1870, the quantities of non-nitrogenized food were carefully noted; and it may be interesting to speculate with regard to the possible influence of such matters upon the production of heat and work. I must premise, however, what I shall have to say upon this point, with the statement that I cannot accept the estimates given of the force used in circulation, respiration, and the production of animal heat, as even approximatively correct. With this reservation, I propose to discuss these estimates, and see what possible relation they bear to food, including non-nitrogenized as well as nitrogenized matters. Weston walked, under my observation, three hundred and seventeen and one-half miles in five consecutive days. Making my calculations according to the method employed by Dr. Pavy, the force-value of his nitrogenized food, during these five days, was 2,858.79 foot-tons. The force-value of his loss of weight, calculated as muscular tissue, was 1,764.52 foot-tons. During the five days, he took non-nitrogenized food which represented 19,521.41 heat-units. All these represent the sum of the sources of power and heat, with which Weston was to accomplish his walk of three hundred and seventeen and one-half miles and maintain circulation, respiration, animal temperature, etc. Non-nitrogenized Food taken by Weston during his Five Days' Walk. I have calculated the heat-units from Letheby's table (On Food, pp. 94, 95). In the table above, I have given the amounts of oatmeal-gruel taken, and I have estimated two ounces of oatmeal for a pint of gruel. In my calculations of the force-value of nitrogenized food, I have already estimated milk, bread, oatmeal, potatoes, and butter, taking the proportion of nitrogen for each of these articles. I have not included sugar before in any of my calculations. 2 The walk of three hundred and seventeen and onehalf miles, according to Dr. Pavy's calculation, was equal to 4,321-33 foot-tons of work. According to Letheby, the force expended daily in circulation and respiration amounts to about 600,000 foot-pounds, or 3,000,000 foot-pounds (1,339.29 foot-tons 1) in five days. Direct observations have shown that the production of heat per pound-weight of the body per hour, in a state of rest, equals 1.283 heat-units. This gives 30.8 heat-units per pound-weight of the body for twentyfour hours, and 3,557-4 heat-units daily for 115.5 lbs. (Weston's average weight for the five days), and 17,787 heat-units for five days. The heat-units represented by the non-nitrogenized food taken during these five days amounted to 19,521 41. Deducting the estimated heat produced by the body, we have remaining an excess of 1,734.41 heat-units, which can be calculated as equal to 597.75 foot-tons of force. These calculations show the following forcevalue represented by all the food and the loss of weight of the body, exclusive of the part of the non-nitrogenized food used in the production of 17,787 heat-units: 1 LETHEBY, On Food, New York, 1872, p. 96. * DALTON, Human Physiology, Philadelphia, 1875, p. 302. I calculate the heat-unit as the quantity of heat required to raise one pound of water from 0° to 1° Fahr. and have reduced the calculations from kilogrammes to pounds and from centigrade to Fahrenheit degrees of the thermometer. Force-value of nitrogenized food....... 2,858.79 foot-tons. 66 66 "loss of weight of the body...... 1,764-52 The actual work represented by walking three hundred and seventeen and one-half miles is estimated at 4,321 33 foot-tons. This leaves 439.56 foot-tons of work which cannot be accounted for in any way, according to the estimates of the observers whom I have quoted, leaving a deficiency of a little more than ten per cent. These calculations show the fallacy of such estimates and the impossibility of accounting for muscular work actually performed, even when we include the heat-value and the force-value of non-nitrogenized food. The estimates of the force used in circulation and respiration and of the heat produced by the body are all calculated for a condition of rest. It is well known, however, that such unusual violent exertion as was made by Weston during his five days' walk would necessarily increase the labor of the heart and respiratory muscles and also produce a very much greater amount of heat than during rest. This would give a much greater deficiency than is shown by the estimates I have made. |