52 THEORY OF EXERCISE. 



ligaments, and bones), but extends to the entire system. 

 Exercise quickens the circulation of the blood, by which 

 means development of tissue is promoted, and secretion and 

 excretion are stimulated. By stimulating the circulation 

 of blood in the surface of the body and by quickening the 

 action of the lungs, exercise entails a loss of water from 

 the system proportionate to its severity, as we may see from 

 the following results obtained from experiments made by 

 Grandeau : 



Amount of water evaporated 

 per day. 



At rest 6.4 Ib. 



Walking, exercise . . . . . . 8.6 ,, 



,, , work 12.7 ,, 



Trotting, exercise ...... 13.4 ,, 



,, , work , 20.6 ,, 



These amounts would of course be greatly influenced 

 by differences in temperature. Under ordinary conditions, 

 the quantity of water removed from the system by the kidneys 

 (in the form of urine) is on an average about double that 

 given off by the lungs and skin ; a difference which exercise 

 tends to reverse. For instance, during severe exertion, the skin 

 of a man may give off two and a half times the quantity 

 of water which is discharged in the urine. The increased 

 activity of the skin and lungs during exercise is essential 

 to health, for removing the extra heat and carbonic acid 

 caused by work. Exercise increases the bodily temperature, 

 which may experience a rise even up to 5 F. from severe 

 work in hot weather ; such an increase of heat being naturally 

 accompanied by more or less exhaustion. As the drinking of 

 water promotes perspiration ; we may conclude, especially as 

 theory in this case is backed up by practical experience, that 

 horses during labour should not be deprived of water for a long 

 time. We all no doubt have enjoyed the refreshing effect of a 

 drink of water or of a fluid largely consisting of water, when we 



