The average date of cessation of menstruation may be regarded as the fixed time from which to estimate the duration of the pre-cessation and post-cessation periods of the menopause. The duration of the pre-cessation period—or the dodging-time, as it is popularly termed—is subject to many and extreme variations. Tilt10 places the limits of normal variation between a few months and six or seven years. The average length of the dodging-time in 275 cases Tilt estimates at two years and three months. The same observer claims to have seen cases of morbid prolongation of the pre-cessation period through ten and even twelve years. Equally variable and indefinite, in point of duration, is the post-cessation period. From the study of his 500 cases, Tilt concludes that cessation of menstruation divides involution into two periods of nearly equal length when no disease of the uterus or adnexa is present. In 383 cases, three or four years after cessation all functional disorders due to the menopause disappeared. But the length of the post-cessation period, as in the case of the dodging-time, is liable to abnormal protraction. Tilt is very positive in the assertion that disturbances directly traceable to the menopause may continue ten or twelve years after cessation of menstruation. The statistical evidence adduced by Tilt in support of his peculiar views as to the possible protraction of the pre-cessation and post-cessation periods (twenty to twenty-four years) may well be questioned. His analysis of cases does not indicate rigid scrutiny. The line between merely coincident phenomena and disorders which are directly traceable to the menopause is nowhere clearly and distinctly drawn. Robert Barnes11 is of the opinion that the average duration of the change of life, comprehending the pre-cessation and post-cessation periods, is from two to three years—an estimate more in accord with the experience of the majority of clinicians.
10 The Change of Life, 4th ed., p. 46 et seq.
11 Diseases of Women, 1878, p. 287.
THE NATURAL HISTORY OF THE CHANGE OF LIFE.—In order to gain an adequate conception of the dynamic disorders in connection with the menopause, it is necessary to bear clearly and distinctly in mind the alterations in functional activity of a purely physiological character which attend that event. Many of the so-called functional disorders of the change of life are merely physiological processes consequent upon the transition from active ovario-uterine life to sexual decrepitude. There is nothing remarkable in the fact that the cessation of menstruation and ovulation, after functional activity of an average period of time varying from thirty to thirty-five years, is sometimes attended by a series of disturbances of a local and constitutional character. The changes of functional activity under these conditions are in analogy to the course and constitution of nature as observed in connection with dentition, puberty, and other epochs in human life.
The physiology of the menopause is a subject extremely difficult of investigation. The reasons are obvious. Our knowledge of the nature and significance of the function of ovulation and menstruation is very defective. The phenomena in connection with the change of life are numerous and complex. All interpretations of the appearances are peculiarly liable to fallacies and unavoidable sources of error. Correction and confirmation by anatomical research are usually impossible. Then the number of recorded cases in which the phenomena have been rigidly analyzed is very limited. But, despite the difficult nature of the subject and the poverty of the literature, a solid nucleus of acquired truth exists. Familiarity with these definitely established facts will clear up many obscure points in the pathology of the menopause.
RESPIRATORY CHANGES. The researches of Andral and Gavarret12 indicate that the quantity of carbonic acid exhaled by the lungs during the second infancy (eight years to puberty) is increased in man and woman. With the establishment of menstruation the quantity of carbonic acid exhaled by the female becomes constant, and persists in this state throughout her menstrual life. During the pre-cessation period the quantity of carbonic acid exhaled by the lungs is rapidly augmented, attaining its maximum about the time of cessation. During the post-cessation period the quantity gradually diminishes until the resettlement of health is effected. After this period it remains relatively constant. In the male, on the other hand, the quantity of carbonic acid exhaled increases up to the thirtieth year, and then progressively diminishes until the end of life.
12 "Recherches sur la quantité d'Acide carbonique exhalé par les Poumons dans l'Éspèce humaine," Annales de Chimie et de Physique, 3e Série, t. viii.
During pregnancy the amount of carbonic acid exhaled is approximately the same as at the time of cessation.
Aran13 recognizes in this augmented excretion of carbonic acid during the change of life a critical or compensating discharge—a waste-gate or outlet, to use the figurative expressions of Tilt and Barnes, for the energy set free in the system by the more or less suddenly suppressed functions of ovulation and menstruation. Gallard,14 on the other hand, has pointedly called attention to the fact that the menstrual blood carries out of the system a quantity of carbonic acid which during pregnancy and change of life is excreted by the lungs—that, accordingly, the increased exhalation of carbonic acid during the climacterium cannot be regarded in the light of a critical discharge.
13 Leçons cliniques sur les Maladies de l'Utérus et de ses Annexes, Paris, 1858-60, p. 284.