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’Annee 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 vertebrae, 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 Gynaecology 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.