des Sciences Médicales, Art., "Menstruation," p. 694) speak of intermenstrual symptoms, and even actual flow, as occurring in women who are in a perfect state of health, and constituting genuine "règles surnuméraries." The condition is, however, said to have been first fully described by Valleix; then, in 18725 by Sir William Priestley; and subsequently by Fehling, Fasbender, Sorel, Halliday Croom, Findley, Addinsell, and others. (See, for instance, "Mittelschmerz," by J. Halliday Croom, Transactions of Edinburgh Obstetrical Society, vol. xxi, 1896. Also, Krieger, Menstruation, pp. 68–69.) Fliess (Die Beziehungen zwischen Nase und weiblichen Geschlechts-Organen, p. 118) goes so far as to assert that an intermenstrual period of menstrual symptoms—which he terms Nebenmenstruation—is "a phenomenon well known to most healthy women." Observations are at present too few to allow any definite conclusions, and in some of the cases so far recorded a pathological condition of the sexual organs has been found to exist. Rosner, of Cracow, however, found that only in one case out of twelve was there any disease present (La Gynécologie, June, 1905), and Storer, who has met with twenty cases, insists on the remarkable and definite regularity of the manifestations, wholly unlike those of neuralgia (Boston Medical and Surgical Journal, April 19, 1900). There is no agreement as to the cause of Mittelschmerz. Addinsell attributed it to disease of the Fallopian tubes. This, however, is denied by such competent authorities as Cullingworth and Bland Sutton. Others, like Priestley, and subsequently Marsh (American Journal of Obstetrics, July, 1897), have sought to find the explanation in the occurrence of ovulation. This theory is, however, unsupported by facts, and eventually rests on the exploded belief that ovulation is the cause of menstruation. Rosner, following Richelet, vaguely attributes it to the diffused hyperæmia which is generally present. Van de Velde also attributes it to an abnormal fall of vascular tone, causing passive congestion of the pelvic viscera. Others again, like Armand Routh and MacLean, in the course of an interesting discussion on Mittelschmerz at the Obstetric Society of London, on the second day of March, 1898, believe that we may trace here a double menstruation, and would explain the phenomenon by assuming that in certain cases there is an intermenstrual as well as a menstrual cycle. The question is not yet ripe for settlement, though it is fully evident that, looking broadly at the phenomena of rut and menstruation, the main basis of their increasing frequency as we rise toward civilized man is increase of nutrition, heat and sunlight being factors of nutrition. When dealing with civilized man, however, we are probably concerned not merely with general nutrition, but with the nervous direction of that nutrition.
At this stage it is natural to inquire what the corresponding phenomena are among animals. Unfortunately, imperfect as is our comprehension of the human phenomena, our knowledge of the corresponding phenomena among animals is much more fragmentary and incomplete. Among most animals menstruation does not exist, being replaced by what is known as heat, or œstrus, which usually occurs once or twice a year, in spring and in autumn, sometimes affecting the male as well as the female.[87] There is, however, a great deal of progression in the upward march of the phenomena, as we approach our own and allied zoölogical series. Heat in domesticated cows usually occurs every three weeks. The female hippopotamus in the Zoölogical Gardens has been observed to exhibit monthly sexual excitement, with swelling and secretion from the vulva. Progression is not only toward greater frequency with higher evolution or with increased domestication, but there is also a change in the character of the flow. As Wiltshire,[88] in his remarkable lectures on the "Comparative Physiology of Menstruation," asserted as a law, the more highly evolved the animal, the more sanguineous the catamenial flow.
It is not until we reach the monkeys that this character of the flow becomes well marked. Monthly sanguineous discharges have been observed among many monkeys. In the seventeenth century various observers in many parts of the world—Bohnius, Peyer, Helbigius, Van der Wiel, and others—noted menstruation in monkeys.[89] Buffon observed it among various monkeys as well as in the orang-utan. J. G. St. Hilaire and Cuvier, many years ago, declared that menstruation exists among a variety of monkeys and lower apes. Rengger described a vaginal discharge in a species of cebus in Paraguay, while Raciborski observed in the Jardin des Plantes that the menstrual hæmorrhage in guenons was so abundant that the floor of the cage was covered by it to a considerable extent; the same variety of monkey was observed at Surinam, by Hill, a surgeon in the Dutch army, who noted an abundant sanguineous flow occurring at every new moon, and lasting about three days, the animal at this time also showing signs of sexual excitement.[90]
The macaque and the baboon appear to be the non-human animals, in which menstruation has been most carefully observed. In the former, besides the flow, Bland Sutton remarks that "all the naked or pale-colored parts of the body, such as the face, neck, and ischial regions, assume a lively pink color; in some cases, it is a vivid red."[91] The flow is slight, but the coloring lasts several days, and in warm weather the labia are much swollen.
Heape[92] has most fully and carefully described menstruation in monkeys. He found at Calcutta that the Macacus cynomolgus menstruated regularly on the 20th of December, 20th of January, and about the 20th of February. The Cynocephalus porcaria and the Semnopithecus entellus both menstruated each month for about four days. In the Macaci rhesus and cynomolgus at menstruation "the nipples and vulva become swollen and deeply congested, and the skin of the buttocks swollen, tense, and of a brilliant-red or even purple color. The abdominal wall also, for a short space upward, and the inside of the thighs, sometimes as far down as the heel, and the under surface of the tail for half its length or more, are all colored a vivid red, while the skin of the face, especially about the eyes, is flushed or blotched with red." In late gestation the coloring is still more vivid. Something similar is to be seen in the males also.
Distant, who kept a female baboon for some time, has recorded the dates of menstruation during a year. He found that nine periods occurred during the year. The average length between the periods was nearly six weeks, but they occurred more frequently in the late autumn and the winter than in the summer.[93]
It is an interesting fact, Heape noted, that, notwithstanding menstruation, the seasonal influence, or rut, still persisted in the monkeys he investigated.
In the anthropoid apes, Hartmann remarks that several observers have recorded periodic menstruation in the chimpanzee, with flushing and enlargement of the external parts, and protrusion of the external lips, which are not usually visible, while there is often excessive enlargement and reddening of these parts and of the posterior callosities during sexual excitement. Very little, however, appears to be definitely known regarding any form of menstruation in the higher apes. M. Deniker, who has made a special study of the anthropoid apes, informs me that he has so far been unable to make definite observations regarding the existence of menstruation. Moll remarks that he received information regarding such a phenomenon in the orang-utan. A pair of orang-utans was kept in the Berlin Zoölogical Gardens some years ago, and the female was stated to have at intervals a menstrual flow resembling that of women, and during this period to refrain from sexual congress, which was otherwise usually exercised at regular intervals, at least every two or three days; Moll adds, however, that, while his informant is a reliable man, the length of time that has elapsed may have led him to make mistakes in details. Keith, in a paper read before the Zoölogical Society of London, has described menstruation in a chimpanzee; it occurred every twenty-third or twenty-fourth day, and lasted for three days; the discharge was profuse, and first appeared in about the ninth or tenth year.[94]
What is menstruation? It is easy to describe it, by its obvious symptoms, as a monthly discharge of blood from the uterus, but nearly