Abstract
Evidence is brought forward of the identity of theelol (C18H24O3) (prepared by Doisy from pregnancy urine) and trihydroxy-oestrin (same formula) (prepared by Marrian) and the fol-licular "hormone hydrate" of Butenandt. The distinguishing activities of these substances have been determined by varying types of assay techniques. Emmenin, which has been prepared from the placenta by Collip and Browne, is in all probability identical with these substances. In these findings lies the proof that the follicular hormone of pregnancy urine is formed as such in the body.