MENSTRUATION. Normal menstruation consists in the escape of from 4 to 6 oz. of blood together with mucus from the uterus at intervals of 28 days (more or less). Menstrual blood does not coagulate under ordinary circumstances. The flow begins at the age of puberty, the average age of which in England is between 14 and 16 years. It ceases between 45 and 5o years of age, and this is called the menopause or climacteric period, com monly spoken of as "the change of life." Both the age of puberty and that of the menopause may supervene earlier or later accord ing to local conditions. Very rarely the menstrual flow may be replaced by haemorrhage from distant organs (epistaxis, haemate mesis, haemoptysis) ; this is called vicarious menstruation. Men struation is closely associated with ovulation (see EMBRYO) .
The usual disorders of menstruation are : amenorrhoea (absence of flow) , dysmenorrhoea (painful flow), (3) menor rhagia (excessive flow), (4) metrorrhagia (excessive and irreg ular flow).
Amenorrhoea may arise from physiological causes, such as pregnancy, lactation, the menopause; constitutional causes, such as phthisis, anaemia and chlorosis, febrile disorders, some chronic intoxications, such as morphinomania, and some forms of cerebral disease; local causes, which include malformations or absence of one or more of the genital parts, such as absence of ovaries, uterus or vagina, atresia of vagina, imperforate cervix, disease of the ovaries, or sometimes imperforate hymen. The treatment of amenorrhoea must be directed towards the cause. In anaemia and phthisis menstruation often returns after improvement in the general condition, with good food and good sanitary conditions, an outdoor life and the administration of iron or other tonics. In local conditions of imperforate hymen, imperforate cervix or ovarian disease, surgical interference is necessary. Amenorrhoea is permanent when due to absence of the genital parts.
The causes of dysmenorrhoea (see WOMEN, DISEASES OF) are classified as follows: (I) ovarian, due to disease of the ovaries or Fallopian tubes; (2) obstructive, due to some obstacle to the flow, as stenosis, flexions and malpositions of the uterus, or malforma tions ; (3) congestive, due to subinvolution, chronic inflammation of the uterus or its lining membrane, fibroid growths and polypi of the uterus, cardiac or hepatic disease; (4) neuralgic ; (5) membranous. The foremost place in the treatment of dysmenor
rhoea must be given to aperients and purgatives administered a day or two before the period is expected. By this means conges tion is reduced. Hot baths are useful, and various drugs. Medic inal treatment is, however, only palliative, and flexions and mal positions of the uterus must be corrected, stenosis treated by dilatation, fibroid growths if present removed, and endometritis when present treated by local applications or curetting according to its severity.
Menorrhagia (see WOMEN, DISEASES OF) signifies excessive bleeding at the menstrual periods. Constitutional causes are pur pura, haemophilia, excessive food and alcoholic drinks and warm climates ; while local causes are congestion and displacements of the uterus, endometritis, subinvolution, retention of the products of conception, new growths in the uterus such as mucous and fibroid polypi, malignant growths, tubo-ovarian inflammation and some ovarian tumours.
Metrorrhagia is a discharge of blood from the uterus, inde pendent of menstruation. It always arises from disease of the uterus or its appendages. Local causes are polypi, retention of the products of conception, extra uterine gestation, haemorrhages in connection with pregnancy, and new growths in the uterus.
In the treatment of both menorrhagia and metrorrhagia the local condition must be carefully ascertained. When pregnancy has been excluded, and constitutional causes treated, efforts should be made to relieve congestion. Uterine haemostatics, as ergot, er gotin, tincture of hydrastis or hamamelis, are of use, together with rest in bed. In uncomplicated uterine haemorrhage local treatment with radium is very beneficial. Fibroid polypi and other new growths must be removed. Irregular bleeding in women over years of age is frequently a sign of early malignant disease, and should on no account be neglected. (See also GYNAECOLOGY.) MENSURATION, that branch of mathematics which deals with the quantitative measurement of length, areas and volumes; or, in a more limited sense, with so much of this subject as is not ordinarily treated under Geometry or Trigonometry. Mensura tion of continuous graphs, i.e., of figures which may be regarded as traced out by a moving ordinate, is usually known as Quad rature (see §6). The present article mainly gives formulae, with out proofs.