Small Intestine

The small intestine continues digestion and absorbs nutrients. Western tradition places the intestines under Virgo, the sign of sorting and assimilation, and the correspondence is a good fit for what the organ does, though it was arrived at from the sign's general character rather than from physiology. In Chinese medicine the small intestine, xiao chang, is the fu paired with the heart and belongs to the fire phase, and its stated function is the separation of the pure from the impure, sending the clear upward and the turbid down to the large intestine and bladder. That the heart should be paired with the small intestine looks arbitrary from a western standpoint and is entirely consistent within the five-phase scheme, which is precisely the point: the pairings follow the phases, not the anatomy.

Ayurveda assigns digestion in the small intestine chiefly to Pachaka Pitta, the same seated digestive fire noted for the gall bladder and stomach, treating the whole upper digestive tract as the working ground of one subdosha rather than dividing its function organ by organ as the Chinese scheme does. The small intestine also carries a documented piece of surgical history distinct from either tradition: successful resection and repair of the small bowel, difficult because of the risk of infection before antisepsis, became reliably survivable only in the later nineteenth century, following the antiseptic techniques introduced by Joseph Lister from 1867, a comparatively recent achievement given how ancient the organ's symbolic and theoretical history is.

Sources Christian AstrologyWilliam Lilly with The Roots of Ayurveda: Selections from Sanskrit Medical WritingsDominik Wujastyk

Among the six fu, the Small Intestine is paired with the Heart in the Fire phase, which is the least intuitive pairing in the whole scheme and one the tradition does not much explain. The channels connect and the phase requires a yang partner for the Heart; that is most of the argument.

The function assigned to the organ is stated in a single phrase that recurs throughout the classical literature: it separates the pure from the impure. It receives what the Stomach has broken down, sends the usable portion onward for the Spleen to transform and distribute, and passes the residue to the Large Intestine and the Bladder. Because the same phrase serves for a mental operation as well as a bodily one, the classics extend the organ's remit to discernment, to the sorting of what is worth keeping from what is not.

That double use is characteristic. Chinese medicine does not maintain separate vocabularies for physical and mental function, and the atlas records the fact rather than resolving it, since the ambiguity is in the sources and not in the translation.

The western scheme places the intestines under Virgo, treated separately. Neither account is an anatomical claim about the small intestine and neither is clinical guidance.