AMNIOS, or Amnion, in Anatomy, the innermost Membrane, wherewith the Fetus in the Womb is immediately invested. See FETUS. The Amnios is a white, soft, thin, transparent Membrane; making part of the Secundines, and lying next under the Chorion. See SECUNDINE, and CHORION. It contains a limpid Liquor, like a thin Jelly-broth; with which the Stomach of the Fetus being always found full, it is supposed to be the Matter of its Nourishment. See NUTRITION. On its outside lies the Allantois, or Urinary Membrane. In some Subjects, the Urinary Membrane, and Chorion stick so close to one another, that they appear to be but one. It hath all its Vessels from the same Origin as the Chorion. See ALLANTOIS. The Word is derived from the Greek amnios, a Lamb; and Pellis Agnina.