+----------------+--------+---------------------------------------+--------+ | | Total | Rates per Hour. | | | | Amount +-------------------+-------------------+ Average| | Kind of | of Heat| Day Periods. | Night Periods. | for | | Experiment. | in 24 | | | 24 | | | Hours. +---------+---------+---------+---------+ Hours. | | | |7 A.M. to|1 P.M. to|7 P.M. to|1 A.M. to| | | | | 1 P.M. | 7 P.M. | 1 A.M. | 7 A.M. | | +----------------+--------+---------+---------+---------+---------+--------+ | |calories| calories| calories| calories| calories|calories| |Rest experiments| 2262 | 106.3 | 104.4 | 98.3 | 67.9 | 94.3 | +----------------+--------+---------+---------+---------+---------+--------+ |Work experiments|} | | | | | | | Heat eliminated|} 4225 | 231.7 | 235.6 | 118.1 | 78.4 | 166.6 | | | | | | | | | |Heat equivalent |} | | | | | | | of external |} 451 | 58.5 | 56.8 | ... | ... | ... | | muscular work |} | | | | | | +----------------+--------+---------+---------+---------+---------+--------+ | Total | 4676 | 290.2 | 292.4 | 118.1 | 78.4 | 194.8 | +----------------+--------+---------+---------+---------+---------+--------+ The work done in these experiments was on a stationary bicycle in the calorimeter, and the heat equivalent was calculated from measurements made by an ergometer attached to the bicycle. We are not concerned here with details, but simply with the general question of the influence of muscular work upon the energy exchange of the body. We note that the work of the day periods, 7 A. M. to 7 P. M., resulted, in the several cases brought together under the average figures, in an increased heat production amounting to more than 100 per cent. Further, we observe that in the body, as in all machines, only a fraction of the energy liberated by the accelerated chemical decomposition, or oxidation, was manifested as mechanical work, the larger part by far being heat eliminated and lost. Thus, Zuntz has found that, in man, about 35 per cent of the extra energy of the food used in connection with external muscular work is available for that work. This, however, shows a noticeably higher degree of efficiency than is generally obtainable by the best steam or oil engines. Lastly, attention may be called to the fact that after the work of the day was finished at 7 P. M., the next period of six hours still showed an accelerated metabolism, as contrasted with what took place during absolute rest.