This is the sixteenth book in a series of 21 Brotherhood of Light Courses by C. C. Zain on the Hermetic Sciences, Astrology, Alchemy, Tarot, Kabbalah and the Occult. The book describes the substance and structure of the astral or stellar body. The author describes how natal and progressed aspects in the chart map aerials between various thought-cell structures in the stellar body that pick up energy similar to a radio receiver. Since the positions of the planets in the birth chart indicate the diseases toward which an individual may be predisposed, the natal and progressed planetary configurations of 160 diseases are listed. A detailed description of how to use Astrodynes for measuring the power and harmony of planets, signs and houses in both the natal and progressed chart is provided by the author, who invented the concept. Instructions are given on how to use Astrodynes to determine the source within the stellar or astral body that is responsible for the individual's disease or discomfort. Various Stellar Treatments, which are methods for applying appropriate healing energies to the compartment of the stellar body causing the problem, are discussed.