THEKMAL PHENOMENA OF THE BODY 195 



contact with the body; so is the air in immediate contact 

 with the skin ; and conversely the body may be warmed by 

 contact with anything warmer than itself, a hot-water bottle, 

 for example. It is not, however, necessary that two solid 

 bodies be in actual contact in order that heat may pass from 

 one to the other. A stove warms all the objects in a room, 

 although few of them are touching it; and the human body 

 may lose heat to, or gain heat from, objects at a greater or 

 less distance. The heating of the body by the sun, millions 

 of miles away, clearly shows this fact. 



The loss of heat by evaporation of water or other liquid 

 from the skin may be readily illustrated by the simple experi- 

 ment of blowing a gentle current of cool, dry air over the 

 dry hand and comparing the cooling thus produced with 

 that which results from blowing a similar current against 

 the moistened hand. In the latter case the cooling will be 

 much greater than in the former. Liquids, like ether, which 

 evaporate more rapidly than water will produce even greater 

 feeling of cold on the skin. 



10. The heat account of the body. The body is therefore 

 constantly receiving and constantly giving out heat, just as 

 a bank is constantly receiving and paying out cash. In the 

 bank a cash account is kept, on one side of which is entered 

 the cash received and on the other the cash paid out. The 

 difference between the two sides, known in business as the 

 balance of the account, shows how much cash is on hand at 

 the time of taking the balance. Should the cash unduly 

 accumulate, efforts are made to keep down the balance by 

 increasing loans; should the cash on hand fall below a 

 desired level, active efforts to encourage loans are lessened 

 and the normal desired balance is restored; finally, should 

 there be an unusual demand for cash at the window of the 

 paying teller, for example, a " run on the bank," the bank 

 will borrow from other banks and in this way keep income 

 and outgo of cash approximately equal. 



