(This must not be confused with the true aether of space--that of which matter is the negation.) This invisible part of the physical body is of great importance to us, since it is the vehicle through which flow the streams of vitality which keep the body alive, and without it, as a bridge to convey undulations of thought and feeling from the astral to the visible denser physical matter, the ego could make no use of the cells of his brain.
The life of a physical body is one of perpetual change and in order that it shall live, it needs constantly to be supplied from three distinct sources.
It must have food for its digestion, air for its breathing, and vitality for its absorption.

This vitality is essentially a force, but when clothed in matter it appears to us as a definite element, which exists in all the worlds of which we have spoken.

At the moment we are concerned with that manifestation of it which we find in the highest subdivision of the physical world.

Just as the blood circulates through the veins, so does the vitality circulate along the nerves; and precisely as any abnormality in the flow of the blood at once affects the physical body, so does the slightest irregularity in the absorption or flow of the vitality affect this higher part of the physical body.
Vitality is a force which comes originally from the sun.

When an ultimate physical atom is charged with it, it draws round itself six other atoms, and makes itself into an etheric element.