I may only add, that, _cæteris paribus_, we shall find that the farther that the pregnancy is advanced beyond the third month, and the nearer it approaches to the end of the sixth, the less chance is there of abortion being accompanied, but the greater of its being succeeded, by nervous affection. As there is a diversity in the symptoms, so is there also in the duration of abortion; for, whilst a few hours in many, and not above three days in the majority of cases, is sufficient to complete the process, we find other instances in which it is threatened for a long time, and a number of weeks elapse before the expulsion take place. ∽∽∽∽ _Of the Causes giving rise to Abortion._ Abortion may very properly be divided into accidental and habitual. The exciting causes of the first class may, in general, be easily detected; those giving rise to the second are often more obscure; and, without great attention, the woman will go on to miscarry, until either sterility, or some fatal disease, be induced. In many cases there can be no peculiar pre-disposing cause of abortion: as, for instance, when it is produced by blows, rupture of the membranes, or accidental separation of the decidua: but when it occurs without any very perceptible exciting cause, it is allowable to infer, that some pre-disposing state exists; and this generally consists in an imperfect mode of uterine action, induced by age, former miscarriages, and other causes. It is well known, that women can only bear children until a certain age; after which, the uterus is no longer capable of performing the action of gestation, or of performing it properly. Now, it is observable, that this incapability or imperfection takes place sooner in those who are advanced in life, before they many, than in those who have married and begun to bear children earlier. Thus we find, that a woman who marries at forty, shall be very apt to miscarry; whereas, had she married at thirty, she might have born children when older than forty; from which it may be inferred, that the organs of generation lose their power of acting properly sooner, if not employed, than in the connubial state. The same cause which tends to induce abortion at a certain age in those who have remained until that time single, will also, at a period somewhat later, induce it in those who have been younger married: for in them we find, that, after bearing several children, it is not uncommon to conclude with an abortion; or, sometimes after this incomplete action, the uterus, after a considerable time, recruits, as it were, and the woman carries a child to the full time, after which she ceases to conceive.