In this tumbler I have some water which I have colored with red ink, so as to represent blood. Here is a small glass syringe, such as can be bought for a few cents in any drug store. Now, when I draw this little handle up, you will see how the syringe is filled with this red water, and when I press it down how the water is forced out of the syringe back into the glass. This very clearly illustrates the principle upon which all pumps and steam engines which pump water are made. Even the large fire engine, which throws water such a great distance, is made largely upon this principle. You may possibly have been in the engine room, where the huge pumps force the water into the reservoirs which supply the city with water for drinking and other purposes. From the pumps and the reservoirs there are great pipes which lead the water under the streets to many thousands of houses which compose the city. After the water has been used it is turned into the sewers, runs down into the river and back to the sea, where it is evaporated, rises again in the clouds, and by the wind is carried hundreds of miles over the country. Then it descends again in the form of snow and rain, soaks down through the earth and finds its way again into the springs and great veins of water under the earth, from which it is carried back once more to the city. Thus it is made pure again and again, to be used over and over by the people whom God has created and whom He supplies with water in this way. Now, in somewhat the same way, the heart, which is both an engine and a pump, forces the blood out through the pipes or tubes of our bodies called the arteries, distributing it to every portion of the body, furnishing the materials for building and renewing the muscles and the bones and every portion of our system. Then gathering up that which is worn out and no longer of service, the impure blood returns through the veins back to the right side of the heart, where it is pumped into the lungs and purified by being brought into contact with the air we breathe. The blood is then returned to the left side of the heart, pumped again into the arteries and distributed through all parts of the body, and so it goes on circulating. Thus the blood is pumped by the heart into the arteries and is distributed to all portions of the body, and returned again to the heart, from fourteen to twenty times each hour of our life.