Mind
While 70% of the body is water, the mind actually envelopes the body and also dwells within.
Your mind is not an entity. The mind is the substratum of your ego. The mind hosts and protects the ego. The ego identifies itself through the mind as separate from God. We, the souls who occupy the body are higher than the mind and the ego.
When we submit ourselves to the mind and the ego, the mind which is present in every cell in the body vibrates at a lower frequency and so we suffer dis-ease, discomfort and illness.