am'nion

[G.] The inner of the membranes composing the sac, bag of waters, which envelops the fetus in the uterus. It consists of two layers, an inner or epiblastic, the true amnion, and an outer or mesoblastic, the false amnion. The latter, which is in contact with the chorion, either unites with that or disappears. The sac lined by the amnion contains the liquor amnii in which the fetus floats.