Abstract Lapidaries, or books on stones, formed a historical literary genre which compiled information on the nature and properties of various stones together with their therapeutic applications. One of the mythical stones described in these lapidaries is the Cock Stone or Alectorius. For the most part, authors agree upon both its origins inside the body and its therapeutic uses, although opinion differs as to the exact organ from which it was obtained. It may represent a biliary calculus. The healing properties cited for the Cock Stone are, at first sight, unrelated. However, when viewed in the light of modern physiological understanding, the pharmacological properties ascribed to Alectorius may be related to the effects of parasympathomimetic substances.