NO. 6 BODY RADIATION ALDRICH 25 



the decrease being greatest on the side facing the wind and about 

 one half as great on the side away from the wind. The clothing tem- 

 perature drop on the side towards the wind is about one third greater 

 than the corresponding skin temperature drop. Summary of lO 

 subjects : 



Skin temp, drop— Clothing temp. drop- 



Air motion Away from Towards Away from Towards Perpendicular 



(ft. per min.) wind wind wind wind to wind 



o to 100 — ?4 — ?8 — ?6 — i?3 — ?5 



100 to 250 —.7 — 1.2 —.4 — 1.7 —.5 



(8) At normal indoor temperature, in still air and with the subject 

 normally clothed and at rest, body heat losses are distributed as 

 follows : 



Evaporation of water 24% 



Radiation 46% 



Convection 30% 



(9) Tests with the thermoelement show that the air temperature 

 falls to room temperature very rapidly as the distance from the body 

 increases. That is, there is a steep temperature gradient in the first 

 centimeter or so from the body surface. With the thermoelement 

 30 cm. away no effect of the presence of the body could be detected. 



(10) The Abbot-Benedict work (table A) indicates that the radia- 

 tion loss from a nude subject is about twice as great for a room 

 temperature of 15° as it is for a room temperature of 26? This evi- 

 dence does not entirely support the " suit of clothes " theory referred 

 to by Du Bois. In explanation of this theory, he says (p. 385, 1927 

 ed. " Basal Metabolism") : "A constriction of the peripheral blood 

 vessels (occurs) and the amount of heat carried to the surface is rela- 

 tively small in proportion to the heat produced. . . . The patient 

 really changes his integument into a suit of clothes and withdraws 

 the zone where the blood is cooled from the skin to a level some 

 distance below the surface." 



(11) Normal fluctuations in humidity indoors produce negligible 

 effect upon the radiation loss. This is to be expected. Our bodies, 

 about 300° Absolute, radiate almost wholly between the wavelengths 

 4ja and S^p- with a maximum at lO/t. Water vapor absorption is so 

 strong for much of this range and so nearly negligible near the maxi- 

 mum, lO/x. that its possible effect is nearly fully produced even by the 

 humidity of an ordinary room. Thus the effect of changes of quan- 

 tity of water vapor in the ordinary room is small. Were the air of the 

 room exceedingly dry, changes might be noticeable. 



