The stomach receives food and begins its breakdown. Western medical astrology associates it with Cancer, the Moon-ruled sign of the stomach and breast, and in the planetary scheme the digestive faculty is generally shared between the Moon and Jupiter. In Chinese medicine the stomach, wei, is the fu paired with the spleen and belongs to the earth phase, and the two together are called the root of postnatal qi, meaning that everything the body acquires after birth, as distinct from the constitutional essence stored in the kidney, comes through them; the stomach is said to rot and ripen the food and to send its essence to the spleen for transformation. The stomach and spleen pair carries more clinical weight in Chinese practice than almost any other, since digestion is treated as the foundation of the whole.
Ayurveda splits the stomach's work between two subdoshas, Kledaka Kapha, which supplies the moisture that softens food on arrival, and Pachaka Pitta, the digestive fire proper that then breaks it down, a two-stage physiological picture that sits closer to the two-stage rot-and-ripen description of Chinese medicine, noted above, than either tradition's authors could have known, since they developed in isolation from one another. A specific piece of documented medical history belongs to the stomach: the American army surgeon William Beaumont was able to observe digestion directly in the 1820s through a permanent gastric fistula in a patient, Alexis St. Martin, whose stomach wound had never fully closed, producing some of the first direct evidence of how gastric digestion actually works.
Sources Christian AstrologyWilliam Lilly with The Roots of Ayurveda: Selections from Sanskrit Medical WritingsDominik Wujastyk