THE CIRCULATORY SYSTEM. 59 



the right auricle; then through the valve into the 

 right ventricle; then through the pulmonary artery 

 to the lungs ; then through the pulmonary veins to 

 the left auricle; then through the valve into the 

 left ventricle; then through the aorta into many 

 arteries ; then into the capillaries ; then ihto the veins, 



which return it to the heart, 







Three iHvis- ^ nere are really three divisions of the 

 ions of the circulatory system. The first is the 

 course of the blood from the heart 

 through the body for building and repair. The 

 second is its course from the heart through the lungs 

 for its purification. The third is a special course of 

 a part of the blood through the liver. This is 

 called the portal circulation. We see here (18) how 

 several of these prominent veins gather the impure 

 blood from these lower organs in the body, and, 

 gathering into this (20) large vein, this blood is 

 thrown into the liver, where it is partly purified, 

 after which it is again collected by this upper (20) 

 hepatic vein, which turns it, as you see, into the large 

 (16) ascending vein, which goes to the heart. 



Interesting The heart is ' b ? f&F ' the stron g es t 



Facts about the muscular part of the body. No 



Circulation. . . , -, .. -, 



engine in the world, of its size, has 

 so much strength. It beats about 100,000 times per 

 day, 40,000,000 times per year, and in the life-time 

 of an octogenarian 3,000,000,000 times without a 

 stop! Its impulse is not only felt by its throbbing 



