14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8l 



The value of the Total Radiation of the subject is obtained some- 

 what empirically as follows: The total surface area (see Notes on 

 Tables, p. 26) is divided into sections 



skin area, girls 8%, boys 7% 



hair 5% 



clothing, girls 78%, boys 79% 



shoes 9% (if boots, 10% and clothing 78%) 



The average skin radiation per sq. cm., as just determined, is mul- 

 tiplied by the corresponding number of centimeters of exposed skin, 

 and similarly for clothing, hair, and shoe areas, and the sum taken. 

 Since part of this total is ineffective, due to the area between the legs 

 and under the arms not radiating to a full hemisphere of wall, this 

 total radiation is reduced 8%. Dividing this result by the number of 

 sq. m. surface area gives the value recorded under Total Radiation. 



PRELIMINARY CALORIMETER EXPERIMENTS 



The total radiation values of table B appeared much too large when 

 compared with the basal metabolism values. The total energy pro- 

 duction or metabolism must at all times equal the total energy loss. 

 Exclusive of a small loss through urine and faeces and the warming 

 of air and food taken in, there are three ways in which the body loses 

 heat, namely, by radiation, by convection (including conduction), and 

 by evaporation of water from lungs and skin. Du Bois states (Basal 

 Metabolism in Health and Disease, ed. 1927, p. 400) that for a room 

 temperature 22° to 25° C. and relative humidity 30 to 50%, the loss 

 by vaporization of water from lungs and skin is about 24% of the 

 total loss. By analogy with work done on the cooling of wires and 

 blackened spheres we would expect the body convection loss to be at 

 least as great as the radiation loss. For example, on p. 251, Smith- 

 sonian Physical Tables, 7th Ed., McFarlane finds the total loss of 

 least as great as the radiation loss. For example, on p. 251, Smith- 

 to a blackened enclosure at 14'^ is .00266 gram calories per second, or 

 .1596 calories per minute. On page 247 the difference in radiation 

 between a black body at 24° C. and one at 14° is 918 — 801 = 117 

 gram cal. per sq. cm. per 24 hours or .0813 calories per sq. cm. per 

 minute. 



Then the per cent of radiation loss of the blackened sphere (which, 

 to be sure, at these low temperatures radiates decidedly less than the 

 " black body ") is 



.0813 ^ . , ^ 



- ^ = 51%, convection loss = 497to 



It is of course true that the actual energy production of each of the 

 ten subjects was materially greater than that shown by the basal 



