The necessity or desire to stretch comes to us because certain parts of the body are not receiving the proper amount of blood circulation and it is these parts that we stretch at such times. If you have ever been to a ball game, you know, of course, that it has become customary for the crowd, no matter how large, to stretch its legs and arms during the last half of the seventh inning. In fact, that has come to be a fixture at ball games and is universally known as the “stretch inning.” Now, it is not so much the result of a desire to encourage the home team as the natural following out of nature’s laws that originally started this practice. The end of the seventh inning at a ball game generally means that the crowd has been sitting quite still for the greater part of an hour and a half, just long enough for the circulation to become poor in parts of the body, and the custom of stretching at a ball game thus comes from the necessity of getting a little more speed into the action of the heart to increase the blood supply. In other words, the stretching constitutes a mild form of exercise. You will notice the ball players themselves do not stretch themselves in the last half of the seventh inning. They are getting enough exercise without that. It is natural, however, for us to stretch as we wake up from sleep after having lain quietly in one position for one or more hours. It is nature’s way of causing the heart to work faster. What Happens When I Stretch? What happens is simply this. When you stretch your arms and legs, you squeeze the arteries and veins which are a part of your arms and legs, much as happens when you pull on a piece of rubber tubing. The tubing becomes flat instead of perfectly round, and it is not so easy to send water through a flat tube as through a round one. Just so with the heart. It is the heart’s business to send blood through the arteries at all times, and when you make them flat the heart’s job becomes just a little harder, and it goes to work beating just a little faster to overcome this extra difficulty. By that time you are through stretching and the heart is busy pumping blood a little faster than ordinarily, and that is what makes you feel so good after you have stretched. Why Can We Think of Only One Thing at a Time? If you are asking the question intelligently, you must know that to think means to concentrate, and in that sense we can only think of one thing at a time, because it takes all of that part of the brain which is used for thinking for just one thing. To give close attention to any one subject means to turn the entire brain force practically in one direction. To let other things pass through the mind at the same time may appear not to interfere with the one thought, but they do, and our conclusions suffer accordingly.