American pennyroyal, Hedeoma pulegioides, is a fragrant herb, native to America, and generally distributed throughout the temperate portions of North America. It was used by the Indians in the form of decoctions and infusions, and was introduced by them to the settlers, coming thence to the attention of the medical profession. Its chief use at the present time is in the making of the volatile oil distilled therefrom. This plant must not be confused with the pennyroyal of Europe, a small, aromatic herb, Mentha pulegium, common throughout Europe, extending northward to Sweden, eastward to Asia Minor and Persia, and southward to Abyssinia and Arabia. The European pennyroyal, also a common domestic remedy, has fallen into therapeutic neglect by the profession.