Blows, bruises, and other exciting causes of inflammation, are apt to produce cancer; but, in many instances, we can detect no evident local cause acting directly on the part. In the breast, for instance, we frequently perceive cancer commence without the interference of any topical agent. In these cases, however, we may uniformly detect an irregularity or disappearance of the menstrual secretion. It was formerly observed, that the uterus and mammæ exhibited very powerfully the sympathy of equilibrium; and it is upon this doctrine, which it is unnecessary farther to illustrate, that we are to explain the affection of the breast, which so frequently takes place in consequence of the cessation of the menses; for when the active state of the uterus is lost, the action of the mammæ is preternaturally increased, and a species of slow inflammation is induced. It is upon this principle only that we can explain why cancers are so frequent at the cessation of the menses[127]. It is ridiculous to suppose that this discharge acts as a drain to the constitution, and carries off impurities, which would otherwise collect elsewhere, and produce local diseases. The breast is almost the only organ which becomes thus affected without any agent acting directly upon the part alone; for, in most other instances, we may detect the operation of such causes at least as tend to induce simple affections of the same part; but, in both instances, the modus operandi of the cause is alike, only circumstances are somewhat varied. [127] It was supposed, that when the menses were obstructed, the impurities were sent by communicating vessels to the breast, where they lodged, and produced cancer. Vide Vesalii Opera, p. 1092. Fabricius de Tum. p. 118. Le Dran observes, that when schirrus, from any cause, takes place in the breast, before the cessation of the menses, it uniformly becomes more painful when any irregularity of that discharge occurs. Vide Memoires de l’Acad. de Chirurg. Tom. III. p. 22.