The heart says, “I will take care of you; if you will take care of me!”
According to The New People’s Physician the human heart is a hollow muscular organ located in the breast that pumps blood received from the veins into the arteries. The heart beat is regulated in two different ways: the heart muscle itself possesses what is called a rhythmic quality of its own and if removed from the body and placed in proper environment it will go on contracting at about forty beats a minute, and may maintain its natural rhythm indefinitely. The heart in its normal function, however, beats seventy to eighty times a minute, and is responsive to all the calls which the body makes on it. The blood in the course of its circulation traverses three varieties of blood vessels when it leaves the heart.
Blood enters the arteries which from there move through capillaries to feed our tissue (i.e., muscles and skin). Capillaries are arteries that divide again and again, until they finally become so small that they are invisible except through a microscope. They are arranged in the form of a network, the size of the mesh depending on the needs of the particular tissue. The blood flows through the capillaries at the speed of about an inch per minute to join the veins. The capillary bed is the great controlling factor of subcutaneous and muscular circulation. The blood flowing through the capillary vessel holds oxygen, and carries away carbon dioxide and other metabolic end products. Life can continue only if the composition of the blood is kept constant by circulation through the organs that replenish its expendable constituents and rid it of its wastes. So small is the reserve of oxygen contained in the blood and tissues that when the heart stops life goes out, in higher animals in a matter of minutes. The rate of circulation varies at different hours of the day; in the afternoon it is at the maximum; in the early morning hours, when we are asleep it is at its minimum.
The arteries are strong, thick and elastic tubes, whose walls are made up of three distinct layers. The innermost is thin and smooth and allows the blood to flow over it without friction or obstacle; next comes a layer of muscle, which by its contraction can lessen the size of the artery and thus diminish the amount of blood flowing through it; the outermost layer is gifted with great elasticity by which it retains an even pressure on the blood in the vessel, and by its recoil gradually drives it on wards. The artery is surrounded with a bed of loose tissue, which allows it a certain amount of freedom of movement. The muscular middle coat of an artery is an exceedingly important provision of nature. The blood supply to an organ must vary with its demand for blood, and this is not constant. The stomach, for instance, during digestion, when it is manufacturing gastric juice, obviously requires a much larger supply of blood than when it is in the resting state. This variation of the supply depends on the state of contraction of the muscle fibers in the walls of the arteries. If the vessels are narrowed the supply of blood is lessened, and vice versa.
The contraction of the arterial walls has another important effect. If it occurs simultaneously in many arteries throughout the body, by offering resistance to the flow of blood, it must increase the blood pressure. An efficient water supply to a town or to a house can be maintained only if the water pressure is sufficiently high, and the same is true of the supply of blood to all parts of the body. In most arteries the branches communicate freely with those of other arteries, a condition known as anastomosis. In this way, if the blood supply of one trunk artery is cut off the supply can be maintained through another. The largest and thickest artery is the aorta. It is the main trunk artery leading out of the heart and conveying the whole stream of blood from that organ to the various parts of the body. In an adult man it is a tube large enough to accommodate two or even three fingers. It runs upwards out of the heart and then sweeps to the left in a wide curve. At the top of this curve it gives off its first large branches, the vessels going to the head and arms; thereafter it runs downwards, behind the heart, passes through the diaphragm and branches to the stomach and bowels. Lower down it divides into two branches, one going to each leg. In health this huge artery is exceedingly elastic like a very large rubber tube. This is of great importance, since the elasticity acts as a reservoir of power between the heartbeats.
Each beat fills the aorta with blood and expands it. The white blood corpuscles can make their way out of the blood vessels by passing between the cells. This migration is enormously increased in inflammation. Ordinarily the red blood corpuscles do not pass out of the capillaries, but this may occur in inflammation. The presence of capillaries is the cause of the rosy tint of healthy skin and mucous membrane; in blushing more capillaries are flooded with blood. If the capillary network is well-filled with blood, then in contact with cold air the temperature of the blood, and therefore the body, will be lowered. In order to prevent undue heat loss, therefore, nature closes up many of the capillaries by contracting the smaller arteries, and this is the reason of the pallor induced by cold weather. On the other hand, if the weather is warm the skin becomes flushed and the loss of heat greater. This important mechanism for controlling the body temperature can be easily impaired by the common habit of wearing too much clothing. It can also be made more active by training the skin to exposure.
