

MAINTENANCE OF THE BODY TEMPERATURE 369 



Individuals have endured incredibly high temperatures 

 when the conditions have been favorable to free evapora- 

 tion. In the eighteenth century a series of trials was 

 made by three members of the Royal Society of London 

 and they finally achieved the distinction of having 

 remained for a quarter of an hour in an atmosphere at 

 225. Water boils at 212. Their feet were protected by 

 thick straw sandals and it is recorded that one of them 

 blistered his hand by touching his watch chain. A piece 

 of meat was cooked during the experiment by simply 

 exposing it on a plate. The survival of these men and 

 others in similar cases must be due to the presence close 

 to all the surfaces of the body, including the respiratory 

 tract, of a layer of relatively cool air. 



Radiation and Conduction. Heat which escapes from 

 the body to warm the surroundings is transmitted in two 

 ways. A part of it is conducted. By this we mean that 

 it raises the temperature of matter in direct contact 

 with the body and then that of more matter just beyond 

 the first. Heat is conducted from a man's body to the 

 bricks of the cold wall against which he leans. It is 

 conducted to the cold water through which he swims. 

 Some substances are superior conductors of heat and 

 these feel cooler than others of the same temperature. 

 Iron feels colder than wood because it receives heat from 

 the skin at a more rapid rate, the temperatures of the iron 

 and the wood being equal. 



By radiation we mean the very swift departure of heat 

 through space. We radiate heat through the air without 

 heating the air itself to any appreciable extent. Heat 

 may pass from the human body across a room to be 

 absorbed by the frosty window panes. Outdoors it 

 may go into interminable space. The heat which we 

 radiate is often compensated by the heat radiated to us. 

 Two rooms may have the same temperature as deter- 

 mined by thermometers hanging in central locations, but 

 one may seem much cooler than the other if it has cool 

 walls and windows. In this room we radiate heat which 



24 



