INCOME AND EXPENDITURE OF ENERGY 



685 



we get in round numbers 2,520 large calories as the heat given off on 

 the more liberal diet. This corresponds fairly well with the calculated 

 heat-loss (p. 681). 



The table on this page, based on the direct calorimetric observations 

 of Atwater and Benedict, shows the average heat-production in a large 

 number of experiments on several individuals at rest and doing measured 

 amounts of work, with a stationary bicycle, for instance. This was 

 connected with a small dynamo, which transformed the greater part 

 of the work into electrical energy. The electrical energy in its turn 

 was changed into heat, the current passing through a lamp. 



1 he heat-production during the hoiirs of sleep, in the second night 

 period, is much less than in the waking hours of rest, and of course 

 enormously less than in the hours of work. After work the heat pro- 

 duction in the period of sleep is only a little greater than after rest. 



As already indicated (p. 683), it is permissible to calculate the heat- 

 production from the diet, and Rubner has done this for various classes 

 of men, reducing everything to the standard of a body-weight of 

 67 kilos. The fasting man, of 67 kilos body-weight, produces 2,303 calo- 

 ries in the twenty-four hours. The class of brain-workers, represented 

 by physicians and officials, produce only a little more heat than the 

 fasting man, viz., 2,445 calories. The second class, represented by 

 soldiers (presumably in time of peace) and day-labourers (probably of 

 a cautious and conservative type), work up to 2,868 calories. The 

 third class, composed of men who work with machines and other skilled 

 labourers, attain a heat-production of 3,362 calories. The fourth class, 

 typified by miners (who are engaged, usually by the piece and not by 

 the day, in severe and exhausting toil), produce as much as 4,790 calo- 

 ries. In the fifth and last class, represented by lumberers and other 

 out-of-door labourers (who, in addition to excessive exertion, have 

 often to face intense cold), the heat-production rises to 5,360 calories. 

 The diet of ordinary prisoners in Scotland, doing light work, chiefly of 

 a sedentary character, was found to correspond to 3,115, and that of 

 convicts on ' hard labour ' to 3,707 calories. It is a fair presumption 

 that in Scotch prisons the total heat value supplied is not excessive. 

 From the general agreement of calculated results with actual measure- 

 ments we can safely conclude that most healthy adults produce between 

 2,000 and 3,000 large calories (35 to 40 per kilo of body-weight) on a ' rest' 

 day, or a day of light labour, and between 3,000 and 4,000 (45 to 60 per 

 kilo of body-weight) on a day of hard manual work. 



