CHAPTER VII 

 THE CIRCULATION 



132. Function and Composition of Blood. It will be 

 recalled that the tissues composing the body are made up 

 of cells ; that these cells are active and must have food ; 

 that there are several substances necessary to feed the 

 cells (albumin, fat, sugar, water, salt, lime); that some of 

 these substances undergo slow combustion in the tissues ; 

 that this combustion or uniting with oxygen gives rise 

 to carbon dioxid and other waste substances. How is 

 the food taken to the cells, how does the oxygen reach 

 them, and how are the products of combustion removed 

 before they accumulate and do injury to the delicate cells ? 

 These three things are done by the circulation of the 

 blood. We can thus readily see how important the blood 

 is and how, if the circulation is free and strong and 

 reaches every part of the body, it is almost impossible for 

 disease and weakness to occur in the body. 



133. Assist, in imagination, in an experiment of great 

 interest. The artery of a hog or other animal is opened. 

 As the blood escapes the animal weakens ; at last it suc- 

 cumbs, and lies motionless, insensible, without breathing, 

 without any external sign of life. It is only a carcass in 

 appearance ; and in a few seconds, it will be only a carcass 

 in reality. Its life is arrested and will soon be finished 

 for want of combustion in the body excited by oxygenated 

 blood. Without delay, the extracted blood is injected 

 again into the veins of the animal. If the experiment is 

 conducted by skillful hands, you will now assist, as it were, 



82 



