Why Does The Heart Beat?
( Originally Published 1921 )
The question why the heart beats seems to be such a simple one that the answer ought to be found by turning over the pages of any book on physiology. But many pages of the world's history have been written while men have been in search of the answer. There have been two great classes of those who have tried to solve this question. One set of men believed that the origin of the heart beat is in the nerves, and later on another set believed that it was in the muscle. It seems now that neither of them was right, but that the cause of the heart beat is really found in the chemistry of the heart. The best explanation of modern times is that there is some substance, the nature of which we do not entirely understand, that is constantly being formed in certain parts of the heart, and when this substance accumulates in a certain amount it generates the beat of the heart. When the heart beats this substance is used up, and an-other beat does not happen until enough of it is formed again. In that way we have a continuously acting cause producing an intermittent action.
Now there is one spot in the heart where the beat ought to start and spread over the whole organ, but sometimes this chemical activity acts in other places, and we have the heart beat originating sometimes in one part of the heart and sometimes in another. Naturally this results in great disorders, and the study of these disorders constitutes an interesting chapter in what we know about the heart.