The mediator is none other than nitrogen. Nitrogen guides the life into the form or configuration which is embodied in the carbon. Wherever nitrogen occurs, its task is to mediate between the life and the spiritual essence which to begin with is in the carbon-nature. Everywhere — in the animal kingdom and in the plant and even in the Earth — the bridge between carbon and oxygen is built by nitrogen. And the spirituality which — once again with the help of sulphur is working thus in nitrogen, is that which we are wont to describe as the astral. It is the astral spirituality in the human astral body. It is the astral spirituality in the Earth’s environment. For as you know, there too the astral is working — in the life of plants and animals, and so on. (Steiner 2007:25)
STEINER, Rudolf. 2007. The Agriculture Course. (Trans.: George Adams) Shrewsbury: Wilding & Son Ltd.