For spiritual scientific research, the heart is also an extraordinarily interesting organ. You know that our trivial science is inclined to treat knowledge of the heart quite lightly. It looks upon the heart as a pump, a pump that pumps the blood through the body. Nothing more absurd than this can be believed, for the heart has nothing whatsoever to do with pumping the blood; rather the blood is set into activity by the entire mobility (Regsamkeit) of the astral body, of the I, and the heart is only a reflection of these movements.
The movement of the blood is an autonomous movement, and the heart only brings to expression the movement of the blood caused by these forces. The heart is in fact only the organ that expresses the movement of the blood; the heart itself has no activity in relation to this movement of the blood. Contemporary natural scientists become very angry if you speak of this issue.
Many years ago, I think in 1904 or 1905, on a journey to Stockholm, I explained this issue to a natural scientist, a medical man, and he was almost apoplectic about the idea that the heart should no longer be regarded as a pump but that the blood itself comes into movement through its own vitality, that the heart is simply inserted in the general movement of the blood, participating with its beat, and so on.
Source: Rudolf Steiner – GA 205 – Therapeutic Insights: Lecture IV – Dornach, July 2, 1921
Translated by May Laird-Brown