Control Of The Blood Flow Throughout The Body
( Originally Published 1921 )
There is a strong tendency to regard the circulation of the blood as a purely mechanical arrangement, as if the tubes that carried it were like the pipes in a house. As a matter of fact,the blood vessels are living things, capable of and accustomed to motion, and much like the heart. A fact little known and little considered is that there is a beating of the blood vessels at the same time that the heart is beating. In speaking of the development of the heart, I said that it was really only an elaboration of a blood vessel. It is also true that a blood vessel is only a simplified and much elongated heart. So the blood is pumped into the blood vessels from the heart, and then each blood vessel either squeezes the blood along to another place where it is needed or, if it happens to be needed in the place where the blood vessel is, enlarges itself to contain the additional blood required.
Put one hand in cold water and the other hand in hot water, and observe the difference in the amount of blood in the two after a moment's immersion. The cold water has caused the vessels to contract, and the hot water has caused them to expand. I once knew an old nurse who said that she did not need a thermometer when she bathed the babies, because if the water was too cold they got blue, and if it was too hot they got red.
These living blood vessels share equally with the heart the task of circulating the blood, and are to be definitely reckoned with in every person who has heart trouble. Leaving out the few who are suffering from purely mechanical trouble with the heart valves, all the rest are suffering from heart and circulatory disease, and when the circulatory factor is taken care of the heart factor is usually easily handled.
The distribution of the blood throughout the body is of vast importance in the care of heart conditions, because if the blood vessels are relaxed and flabby, the heart has no constant load to carry and becomes irritable. And if on account of high blood pressure and great resistance in the organs the labor of the heart is much increased, it struggles under a load that is too heavy.
Bad as it is to have too little pressure or too much pressure in the blood throughout the body, the worst of all is to have irregular pressure. So in the treatment of people with heart and circulatory disease we strive to have the blood pressure approach the normal ; but failing in this, we try to establish it at a definite level and keep it there, and adjust the whole system to that level. Many have constitutionally low blood pressure, and their hearts must be adjusted to this. Or people with high blood pressure must be adjusted to it. The heart has a greater capacity to adjust itself to variations of pressure than the blood vessels have to adjust their pressure to heart conditions. So the important thing to be sought is an even distribution of the blood throughout the body.