The most important portion of the body is the stomach. If the stomach ceases to work even for a single moment, the whole body would collapse. The work of the stomach is to digest the food, and so to provide nourishment to the body. Its relation [Pg 13] to the body is the same as that of the steam engine to the Railway train. The gastric juice which is produced in the stomach helps the assimilation of nutritious elements in the food, the refuse being sent out by way of the intestines in the form of urine and f ces. On the left side of the abdominal cavity is the spleen, while to the right of the stomach is the liver, whose function is the purification of the blood and the secretion of the bile, which is so useful for digestion. In the hollow space enclosed by the ribs are situated the heart and the lungs. The heart is between the two lungs, but more to the left than the right. There are on the whole 24 bones in the chest; the action of the heart can be felt between the fifth and the sixth rib. The lungs are connected with the windpipe. The air which we inhale is taken into the lungs through the windpipe, and the blood is purified by it. It is of the utmost importance to breathe through the nose, instead of through the mouth. On the circulation of the blood depend all activities of the body. It is the blood that provides nourishment to the body. It extracts the nutritious elements out of the food, and ejects the refuse through the intestines, and so keeps the body warm. The blood is incessantly circulating all over the body, along the veins and the arteries. [Pg 14] The beatings of the pulse are due to the circulation of the blood. The pulse of a normal adult man beats some 75 times a minute. The pulses of children beat faster, while those of old men are slower. The chief agency for keeping the blood pure is the air. When the blood returns to the lungs after one complete round over the body, it is impure and contains poisonous elements. The oxygen of the air which we inhale purifies this blood and is assimilated into it, while the nitrogen absorbs the poisonous matter and is breathed out. This process goes on incessantly. As the air has a very important function to perform in the body, we shall devote a separate chapter to a detailed consideration of the same. Chapter III AIR