It is natural to assume that this connection between the activity of the womb and the glandular activity of the breasts is a nervous connection, by means of the spinal cord, and such a connection certainly exists and plays a very important part in the stimulating action of the breasts on the sexual organs. But that there is a more direct channel of communication even than the nervous system is shown by the fact that the secretion of milk will take place at parturition, even when the nervous connection has been destroyed. Mironoff found that, when the mammary gland is completely separated from the central nervous system, secretion, though slightly diminished, still continued. In two goats he cut the nerves shortly before parturition and after birth the breasts still swelled and functioned normally (Archives des Sciences Biologiques, St. Petersburg, 1895, summarized in L'Année Biologique; 1895, p. 329). Ribbert, again, cut out the mammary gland of a young rabbit and transplanted it into the ear; five months after the rabbit bore young and the gland secreted milk freely. The case has been reported of a woman whose spinal cord was destroyed by an accident at the level of the fifth and sixth dorsal vertebræ, yet lactation was perfectly normal (British Medical Journal, August 5, 1899, p. 374). We are driven to suppose that there is some chemical change in the blood, some internal secretion from the uterus or the ovaries, which acts as a direct stimulant to the breasts. (See a comprehensive discussion of the phenomena of the connection between the breasts and sexual organs, though the conclusions are not unassailable, by Temesvary, Journal of Obstetrics and Gynæcology of the British Empire, June, 1903). That this hypothetical secretion starts from the womb rather than the ovaries seems to be indicated by the fact that removal of both ovaries during pregnancy will not suffice to prevent lactation. In favor of the ovaries, see Beatson, Lancet, July, 1896; in favor of the uterus, Armand Routh, "On the Interaction between the Ovaries and the Mammary Glands," British Medical Journal, September 30, 1899.
While, however, the communications from the sexual organs to the breast are of a complex and at present ill understood character, the communication from the breasts to the sexual organs is without doubt mainly and chiefly nervous. When the child is put to the breast after birth the suction of the nipple causes a reflex contraction of the womb, and it is held by many, though not all, authorities that in a woman who does not suckle her child there is some risk that the womb will not return to its normal involuted size. It has also been asserted that to put a child to the breast during the early months of pregnancy causes so great a degree of uterine contraction that abortion may result.
Freund found in Germany that stimulation of the nipples by an electrical cupping apparatus brought about contraction of the pregnant uterus. At an earlier period it was recommended to irritate the nipple in order to excite the uterus to parturient action. Simpson, while pointing out that this was scarcely adequate to produce the effect desired, thought that placing a child to the breast after labor had begun might increase uterine action. (J. Y. Simpson, Obstetric Memoirs, vol. i, p. 836; also Féré, L'Instinct Sexuel, second edition, p. 132).
The influence of lactation over the womb in preventing the return of menstruation during its continuance is well known. According to Remfry's investigation of 900 cases in England, in 57 per cent. of cases there is no menstruation during lactation. (L. Remfry, in paper read before Obstetrical Society of London, summarized in the British Medical Journal, January 11, 1896, p. 86). Bendix, in Germany, found among 140 cases that in about 40 per cent. there was no menstruation during lactation (paper read before Düsseldorf meeting of the Society of German Naturalists and Physicians, 1899). When the child is not suckled menstruation tends to reappear about six months after parturition.
It is possible that the divergent opinions of authorities concerning the necessarily favorable influence of lactation in promoting the return of the womb to its normal size may be due to a confusion of two distinct influences: the reflex action of the nipple on the womb and the effects of prolonged glandular secretion of the breasts in debilitated persons. The act of suckling undoubtedly tends to promote uterine contraction, and in healthy women during lactation the womb may even (according to Vineberg) be temporarily reduced to a smaller size than before impregnation, thus producing what is known as "lactation atrophy." In debilitated women, however, the strain of milk-production may lead to general lack of muscular tone, and involution of the womb thus be hindered rather than aided by lactation.
On the objective side, then, the nipple is to be regarded as an erectile organ, richly supplied with nerves and vessels, which, under the stimulation of the infant's lips—or any similar compression, and even under the influence of emotion or cold,—becomes firm and projects, mainly as a result of muscular contraction; for, unlike the penis and the clitoris, the nipple contains no true erectile tissue and little capacity for vascular engorgement.[[19]] We must then suppose that an impetus tends to be transmitted through the spinal cord to the sexual organs, setting up a greater or less degree of nervous and muscular excitement with uterine contraction. These being the objective manifestations, what manifestations are to be noted on the subjective side?
It is a remarkable proof of the general indifference with which in Europe even the fairly constant and prominent characteristics of the psychology of women have been treated until recent times that, so far as I am aware,—though I have made no special research to this end,—no one before the end of the eighteenth century had recorded the fact that the act of suckling tends to produce in women voluptuous sexual emotions. Cabanis in 1802, in the memoir on "Influence des Sexes" in his Rapports du Physique et du Moral de l'Homme, wrote that several suckling women had told him that the child in sucking the breast made them experience a vivid sensation of pleasure, shared in some degree by the sexual organs. There can be no doubt that in healthy suckling women this phenomenon is exceedingly common, though in the absence of any methodical and precise investigation it cannot be affirmed that it is experienced by every woman in some degree, and it is highly probable that this is not the case. One lady, perfectly normal, states that she has had stronger sexual feelings in suckling her children than she has ever experienced with her husband, but that so far as possible she has tried to repress them, as she regards them as brutish under these circumstances. Many other women state generally that suckling is the most delicious physical feeling they have ever experienced. In most cases, however, it does not appear to lead to a desire for intercourse, and some of those who make this statement have no desire for coitus during lactation, though they may have strong sexual needs at other times. It is probable that this corresponds to the normal condition, and that the voluptuous sensations aroused by suckling are adequately gratified by the child. It may be added that there are probably many women who could say, with a lady quoted by Féré,[[20]] that the only real pleasures of sex they have ever known are those derived from their suckling infants.
It is not difficult to see why this normal association of sexual emotion with suckling should have come about. It is essential for the preservation of the lives of young mammals that the mothers should have an adequate motive in pleasurable sensation for enduring the trouble of suckling. The most obvious method for obtaining the necessary degree of pleasurable sensation lay in utilizing the reservoir of sexual emotion, with which channels of communication might already be said to be open through the action of the sexual organs on the breasts during pregnancy. The voluptuous element in suckling may thus be called a merciful provision of Nature for securing the maintenance of the child.
Cabanis seems to have realized the significance of this connection as the basis of the sympathy between mother and child, and more recently Lombroso and Ferrero have remarked (La Donna Delinquente, p. 438) on the fact that maternal love has a sexual basis in the element of venereal pleasure, though usually inconsiderable, experienced during suckling. Houzeau has referred to the fact that in the majority of animals the relation between mother and offspring is only close during the period of lactation, and this is certainly connected with the fact that it is only during lactation that the female animal can derive physical gratification from her offspring. When living on a farm I have ascertained that cows sometimes, though not frequently, exhibit slight signs of sexual excitement, with secretion of mucus, while being milked; so that, as the dairymaid herself observed, it is as if they were being "bulled." The sow, like some other mammals, often eats her own young after birth, mistaking them, it is thought, for the placenta, which is normally eaten by most mammals; it is said that the sow never eats her young when they have once taken the teat.
It occasionally happens that this normal tendency for suckling to produce voluptuous sexual emotions is present in an extreme degree, and may lead to sexual perversions. It does not appear that the sexual sensations aroused by suckling usually culminate in the orgasm; this however, was noted in a case recorded by Féré, of a slightly neurotic woman in whom intense sexual excitement occurred during suckling, especially if prolonged; so far as possible, she shortened the periods of suckling in order to prevent, not always successfully, the occurrence of the orgasm (Féré, Archives de Neurologie No. 30, 1903). Icard refers to the case of a woman who sought to become pregnant solely for the sake of the voluptuous sensations she derived from suckling, and Yellowlees (Art. "Masturbation," Dictionary of Psychological Medicine) speaks of the overwhelming character of "the storms of sexual feeling sometimes observed during lactation."