PHYSIOLOGY. Reproductive activity, including the functions of menstruation, conception. gesta tion, parturition, and lactation. is limited in the female to a period of life beginning at about the twelfth year and ending about the forty fifth. These limits vary by a few years. accord ing to climate. an earlier maturity being char acteristic of hot countries. When conception has taken place, the impregnated ovum makes its way through one of the Fallopian tubes to the cavity of the uterus, where it lodges and develops through the agency of a convoluted mass of blood vessels called the placenta. from which a cord of vessels (the umbilical cord) runs to the abdomen of the Rents. The duration of normal pregnancy varies from 275 to 250 days (nine calendar o• ten lanai' months), hut gestation may be prolonged beyond this time in very rare cases to 300 or 306 days. Pregnancy is ter minated with the expulsion of the child by the contractions (labor pains) of the powerful mus cular fihres of the uterus. The more important signs and symptoms of pregnancy are the per ception of the fetal heart-beat.; by the ear (aus cultation) ; 'quickening.' or active movements of the child in stern; passive movements (hallotte inept) elicited by manipulation; suppression of the menses, morning nausea, gradual enlargement of the abdomen and breasts, and pigmentation of the area immediately surrounding the nipple. Of these only the first three can be considered certain indications of pregnancy. the existence of which can rarely he diagnosed with precision before the third month. During gestation the f(etns floats freely in a sae of water called the amniotic tluid, and changes its position fre quently. When parturition begins. however, the long axis of the foetus usually coincides with that of the mother, with the head downward. or presenting at the pelvic outlet. This is by far the most common presentation. occurring in about 96 per cent. of all cases. In about 3 per cent, the buttocks o• feet present. About once in 200 labors what is known as a transverse presenta tion is met with (that is, the long axis of the child is at right angles to that of the mother). Delivery being impossible in this position. artifi cial correction of the presentation, usually by turning and bringing down the feet. must be resorted to. Labor is arbitrarily divided into three stages: Tlw first stage begins with the earliest premonitory pain, and ends with the complete dilatation of the uterine outlet ; this stage may last several hours or even days. Dur ing the second stage the bog of water ruptures, the uterine emitractions beconw stronger, and the child passes through the parturient canal and is born. This event completes the second
stage. The third stage ends with the expulsion of the placenta and fodal membrane, and lasts usually about half an hour. The duration of labor in first confinements is on an average about (melte hours; in succeeding labors, six to eight hours; although much longer periods are not or uncommon. The puerperal or lying-in state begins at the completion of labor and lasts about six weeks. During this lime lactation is inaugurated and the uterus gradually resilines its wonted size and shape (involution). Tice length of the lying-in period varies in different countries and races; among uncivilized people and in parts of the East the mother tesumes her usual occupations immediately after parturition; but in civilized countries the woman is confined to her bed for a week or ten days.
Tut.: P.vr)toLtmv ice PREGNANCY. While the pregnant woman is liable to disease equally with other individuals, there are certain disorders which are peculiarly apt to arise during gesta tion. or are dependent on it. The teeth may undergo devay, owing to the fact that the mineral elements necessary for their nutrition are ap propriated by the embryo. Constipation from both mechanical and sympathetic causes is a volintem disorder. The kidneys, owing to the inpreased functional activity demanded of them, not infrequently la-conie diseased. as evidenced by the appearance of albumen in the urine. These organs failing in their function. poisonous prod ucts of metabolism accumulate in the blood. pro nounced nervous symptoms, such as headaches, vomiting, and impairment of sight and hearing, appear. and if not relieved. uraonie convulsions (the so-called eelampsia) are induced, ending often in coma and death. Besides these and many other a ffect ions incident to pregnancy, there are certain chronie diseases which, lly reason of the increased strain upon the vitality at this time, are likely to prove fatal. The heart moonally under1.404.; a measure of 'hyper trophy in pregnant women ill order to meet the increased demands of circulation. When, how ever. there exists chronic disease either of the substance or the valves of this organ, it may rrGye icner1ual to the strain. The danger from this condition inerease; with each succeeding pregnancy. When pulmonary philmisis exists in the gestation in the majority of eases accelerates the progress of the disease.