If you are interested in exploring Manly P. Hall's work further, I can help you:
He often pairs the pineal gland (the male/positive principle) with the pituitary gland (the female/negative principle). The meeting of the energy from these two glands in the brain represents the spiritual marriage, or inner enlightenment. the pineal gland the eye of god manly p hall pdf link
Manly P. Hall (1901–1990), founder of the Philosophical Research Society and author of the monumental text The Secret Teachings of All Ages , dedicated a significant portion of his life’s work to decoding the hidden symbolism of the human body. Hall pioneered a concept known as "occult anatomy." He argued that the physical human form is a localized reflection of the macrocosm (the universe). If you are interested in exploring Manly P