Take Origin.-From both fœtus and mother, mainly the former. Function.-Distends uterus and protects foetus, affording an equal temperature for it and receiving its secretions. Does not nourish beyond adding to its supply of water. ABNORMALITIES OF THE AMNION. Its pathology is similar to that of all serous membranes, i. e., inflammation, exudations, serous and plastic. (A) Abnormalities of Secretions : Is dis (a) Oligohydramnios.—Rare; 1 in 3000 or 4000 cases. advantageous, because walls of uterus not kept apart and fœtus apt to be injured or deformed. During pregnancy the mother is likely to suffer pain, and labor is usually difficult. (b) Hydramnios.—When two quarts or more of fluid may be present. Occurs about 1 in 250 to 300 cases. Cause.-Production may be increased; absorption may be decreased. It may be the fault of foetus, mother, or both. On the part of the foetus there may be (a) excess of urine; (b) excessive transudation of fœtal serum, from vessels under placental surface, which do not disappear about the third or fourth month when hydramnios exists, or from any condition raising the blood pressure in the umbilical veins, as cirrhosis of the liver (syphilitic), an abdominal tumor, or any abnormality in vascular system of foetus. (c) From fœtal skin. A pathological condition of this is found in some cases, as nævi, elephantiasis congenita cystica. Having its origin in the mother, the hydramnios may be a part of a general dropsy or be due to an exaggerated hydræmia. Very rarely does it arise from both foetal and maternal causes, and a distinct cause cannot always be found. It is most frequently of foetal origin. Diagnosis.-The existence of pregnancy, great movability of the foetus, and the distention of abdomen greater than the period of duration of the pregnancy would account for, are three im\portant signs. When there is a very large amount of fluid the diagnosis is very difficult. It may be mistaken for ovarian cyst, ascites accompanying pregnancy, distended bladder with retroversion of gravid uterus. Classes.-Acute. Rare. There is a sudden transudation of fluid from some traumatism. Symptoms.-Pain, difficulty in respiration, at times orthopnoea, fever. Chronic.-Begins at the third or fourth month and steadily increases, usually causing but little trouble. Treatment.-Immediate evacuation in the acute_variety; in the chronic this is, as a rule, not required. If necessary, the life of the foetus is not to be considered, as it will usually be diseased. Aspiration through uterine wall condemned. The membranes are to be punctured at the os, using the hand as a plug to prevent sudden escape of fluid. (B) Abnormalities of Color and Consistency.-Normally slightly opaque in the latter months of pregnancy, the liquor amnii may be green or brown from the presence of meconium, or tinged with red if the fœtus is macerated. (C) Putrefaction of the Liquor Amnii.-Most likely to be associated with death and decomposition of the foetus, but occasionally there is an intensely putrid odor to the liquor amnii, with physometra, and yet the child is born alive. (D) Plastic Exudation.-Usually occurs early when amnion and foetus are near each other, and thus forms bands of adhesion between them, and even causes amputations of foetal extremities and premature detachment of the placenta. (E) Abnormal Tenuity.-Rare. The amnion may rupture and become separated from the chorion, which remains intact, forming bands or strings by being rolled upon itself. The strings thus formed may encircle the foetus. (F) Cysts. Of no clinical importance. (G) Rupture.-Abortion may result. Occasionally the amnion and chorion are perforated at a situation remote from the internal os, and the liquor amnii dribbles away for some weeks, or even months, before delivery. This is called an amniotic hydrorrhoea. The Chorion. Definition.-The chorion is the outermost of the fœtal mem-` branes, and is formed from the external layer of the non-germi |