THE HUMAN VODY. 



mind are excited by stimulants, to make them forget the 

 need of rest. 



10. Sleep, though the most perfect, is not the only, way 

 of resting. When we have been using the muscles, we 

 may rest them while using the brain. After study, hearty 

 muscular exercise is rest. Entire change of occupation is 

 rest. 



MATERIALS FOR REPAIR. 



SECTION II. 1, The materials by which the waste of 

 the system is repaired, are found in air, food, and water. 

 Air must be taken in constantly, food and water at fre- 

 quent intervals. We can live but a few minutes without 

 air : without water we should perish in a few days. Men 

 have lived without food for weeks, having air and water; 

 but the body must at length be exhausted if these three 

 things are not regularly supplied in sufficient quantity. 



2, We take oxygen from the air by the breathing 

 apparatus. We take food and water by the digestive 

 apparatus. Both are taken into the blood, and carried 

 through the body, to be used as needed in every part. 



3, The blood not only carries the oxygen, food, and 

 water to every part of the body: it also carries away 

 from every part the ivaste matter which is formed there, 

 and delivers it to the organs which discharge it from the 

 body. It has been likened to an express-agent, who goes 

 about the streets of a city, leaving a parcel here, taking 

 one there, his wagon always loaded, though its contents 

 are constantly changing. 



THE BLOOD. 



SECTION III. 1. Blood is a red fluid, not transparent, 

 having a salty taste. It is a little heavier and thicker 



