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 Fere, 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 Duesseldorf 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?