Violent exercise, as dancing, for instance, or much walking, or the fatigueing dissipations of fashionable life, more especially in the earlier months, by affecting the circulation, may vary the distribution of blood in the uterus, so much as to produce rupture of the vessels, or otherwise to destroy the ovum. There is also another way in which fatigue acts, namely, by subducting action and energy from the uterus: for the more energy that is expended on the muscles of the inferior extremities, the less can be afforded or directed to the uterus; and hence abortion may be induced at an early stage of gestation[8]. Even at a more advanced period, inconvenience will be produced upon the principle formerly mentioned; for the nerves of the loins conveying less energy, in many instances, though not always to the muscles, they are really weaker than formerly, and are sooner wearied, producing pain, and prolonged feeling of fatigue, for many days, after an exertion which may be considered as moderate. This feeling must not be confounded with a tendency to abortion, though it may sometimes be combined with it, for generally by rest the sensation goes off. Neither must we suppose that the child is dead, from its being usually quiet during that period, for as soon as the uterus, which has been a little impaired in its action, recovers, it moves as strongly as ever. In the next place, I mention the death of the child, which may be produced by syphilis, or many diseases perhaps peculiar to itself, or by injury of the functions of the placenta. But in whatever way it is produced, the effect is the same in checking the action of gestation, unless there be twins, in which case it has been known that the uterus sometimes did not suffer universally, but the action went on, and the one child was born of the full size, the other small and injured[9]. The length of time required for producing abortion from this cause is various; sometimes it is brought on in a few hours: at other times not for a fortnight, or even longer. In these and similar cases, when the muscular action is commencing, the discharge is trifling, like menstruation, until the contraction becomes greater, and more of the ovum be separated. A third cause is a disproportioned action betwixt the uterus and ovum, the one not increasing in the same ratio with the other, yet both continuing to act. This is productive of frequent discharges of blood, repeated at different, but always at short intervals, for several weeks, until at length the uterus suffers so much, that its action stops, or the fœtus dies. Another cause is, any strong passion of the mind. The influence of fear, joy, and other emotions on the muscular system, is well known; and the uterus is not exempted from their power; any sudden shock, even of the body, has much effect on this organ. The pulling of a tooth, for instance, sometimes suddenly produces abortion.