Note 82 — BOOK XXXII.1 REMEDIES DERIVED FROM AQUATIC ANIMALS.
John Bostock translation
The Castoreum of the ancients, the “castor” of our Materia Medica, is not in reality produced from the testes of the beaver, as was supposed by the ancients, but from two oval pouches situate near the anus of the animal of either sex. There are four of these pouches in all, two containing a species of fat, and two larger ones including in their membranous cells a viscous fetid substance, which forms the castor of medicine. It is considered to be an antispasmodic.