(From involvo, to fold in; from com-ingnextafterthechild). Secundines.hystera, membrane?.

They form an universal covering for the foetus, and the water in which it floats during pregnancy. They consist of the membranes called Chorion, and Amnion; the Placenta, and part of the Funus umbilicalis, vide in verbis.

If in labour the membranes do not break immediately upon their being pushed into the vagina, they should be allowed to protrude still further in order to dilate the os externum. - If they suddenly burst, and dis-charge much water, and the pains soon slacken, the labour becomes tedious. While the head of the child is yet covered with the unbroken membrane, it is smooth, soft, and slippery to the touch. Sometimes when the head presents the fontanel feels puffy, and deceives us, as it is mistaken for the membranes; but this should be carefully distinguished. If during labour the waters push the membranes down in an oblong form, the birth will be tedious. A short broad, or round form is the best.