The Heart in the Human Organism
In lecture five of the Agriculture Course, Rudolf Steiner relates that the stinging nettle plays a role in nature very similar to the working of the heart in the human organism. But how does spiritual science picture the working of the human heart? The heart perceives and balances what occurs between the upper and lower poles of the human organism, that is what lives above and below the diaphragm, the play between the outer planets in the nerve-sense system, and the inner planets in the metabolic system. Already in lecture two of the Agriculture Course we have the image of the upper and lower planets working across the diaphragm of the living soil.
“That tension of opposite forces which we have traced in the plant, that alternation and interplay of super-solar and infra-solar forces, is also manifest in man in the movements of the heart. The heart movements are not only an imprint of what takes place in man, they are also an imprint of extra-human conditions. For in the human heart you may see reflected as in a mirror, the whole process of the universe. Man is individualised merely as a being of soul and spirit. In other aspects of being, he is inserted into the universal process, so that, for instance, the beats of his heart are not only an expression of what takes place within man, but also of that contest between light and gravity that fills the whole cosmic stage.
“For what is the heart after all? It is a sense organ, and even if its sensory function is not directly present in the consciousness, if its processes are subconscious, nevertheless it serves to enable the “upper” activities to feel and perceive the “lower.” As you perceive external colours through your eyes, so do you perceive, dimly and subconsciously through your heart, what goes on in the lower abdomen. The heart is an organ for inner perception.”