It is obvious that a man asleep, or lying quietly at rest, in the calorimeter, especially when he has been without food for some hours, furnishes suitable conditions for ascertaining the minimal energy requirements of the body. Under such conditions, bodily activity and heat output are at their lowest, and we are thus afforded the means of determining what is frequently called the basal energy exchange of the body. The following table taken from Magnus-Levy, and embodying results from many sources, shows the heat production during sleep, calculated for 24 hours, of various individuals of different body-weight and of different body surface. I venture to present these individual results, rather than make a general statement simply, because it is important to recognize the fact that the basal energy exchange differs according to body-weight, extent of body surface, and the condition of the body. In the table, the results are arranged in the order of body-weight, and it is plain to see that the absolute energy exchange is greater with heavy persons than with light, yet the energy exchange does not increase in proportion to increase of body-weight. With a man of 83 kilos body-weight, the basal exchange is only 30–40 per cent higher than in a man of 43 kilos body-weight. In other words, the man of small body-weight has, per kilo, a much higher basal exchange than the heavier man. The energy exchange is more closely proportional to the extent of body surface than to weight. +-------------+----------------+--------------+ | Body-weight | Total Calories | Calories per | | of the | for 24 Hours. | Kilo of | | Individual. | | Body-weight. | +-------------+----------------+--------------+ | kilos | | | | 43.2 | 1333 | 30.9 | | 48.0 | 1214 | 25.3 | | 50.0 | 1315 | 25.9 | | 53.0 | 1527 | 28.8 | | 55.0 | 1590 | 28.9 | | 56.5 | 1519 | 26.8 | | 57.2 | 1560 | 27.3 | | 58.0 | 1510 | 26.0 | | 62.5 | 1431 | 22.9 | | 63.0 | 1418 | 22.5 | | 63.0 | 1492 | 23.7 | | 64.0 | 1656? | 25.8 | | 64.9 | 1475 | 22.7 | | 65.0 | 1498 | 23.0 | | 65.0 | 1445 | 22.2 | | 67.5 | 1608 | 23.8 | | 67.5 | 1621 | 24.0 | | 70.0 | 1661 | 23.7 | | 70.0 | 1620 | 23.1 | | 71.2 | 1787 | 25.1 | | 72.6 | 1550 | 21.3 | | 72.7 | 1657 | 22.8 | | 73.0 | 1584 | 21.7 | | 73.0 | 1630 | 22.4 |