Hyleg
The hyleg is the chart's giver of life, the body chosen by rule from a short list of candidates, which classical medical astrology reads as the source of vitality.
Candidates are taken in order of eligibility: usually the Sun in a day chart and the Moon in a night chart, with the Ascendant and the Lot of Fortune as fallbacks when neither is placed to qualify. The rule is mechanical, which is why two astrologers reading the same chart should find the same hyleg.
Our health reports name the hyleg and pair it with the alcochoden, and they frame both as classical method rather than as any statement about health.
Frequently asked
Is the hyleg always the Sun?
No. It depends on sect and on whether the candidate is placed in a qualifying part of the chart; in many night charts it is the Moon.
Does the hyleg predict lifespan?
Historically it was used that way. We treat it as a classical vitality signature and explicitly not as a medical or predictive claim.