The word abortion, used somewhat loosely, signifies the premature expulsion of the fetus; the expulsion of the fetus from the womb before it is viable, i.e., before it is capable of living independently. Used in a stricter sense, the word abortion is applied to the expulsion of the fetus up to the end of the 16th week; to the expulsion of the fetus between the 16th and the 28th week the term miscarriage is applied; and when the expulsion of the fetus takes place after the 28th week, but before full term, we use the term premature labor. The laity does not like the term abortion, as it is under the impression that the term always signifies criminal abortion; it therefore prefers to use the term miscarriage ("miss"), regardless of the time at which the expulsion of the fetus takes place. When an abortion (or miscarriage) takes place by itself, without any outside aid, we call it _spontaneous abortion_. When it is brought on by artificial means, whether by the woman herself or by somebody else, we call it _induced_ abortion. When an abortion is induced for the purpose of saving the woman's life, we call it _therapeutic_ abortion; this is considered perfectly legal and proper. But where an abortion is induced merely to save an unmarried mother's reputation, or because the married mother is too poor or too weak to have any more children, or is reluctant to have any (or any more) for any other reason, it is called _criminal_ or _illegal_ abortion, and, if discovered, subjects the mother and the person who produced the abortion to severe punishment. When the fetus for some reason dies in its mother's womb, it is generally expelled within a few hours or days. Sometimes this is not the case, and the dead fetus is retained for several weeks, or months or even years; to such a phenomenon we apply the term _missed_ abortion. Some women suffer from what might be called the abortion habit; they can hardly ever carry a child to full term, but lose it in the same month or even in the same week of gestation during each pregnancy; we call this habitual abortion. And this habitual abortion may be independent of disease, such, for instance, as syphilis. The terms _threatened_, _imminent_ and _inevitable_ abortion require no further explanation. =The Causes of Abortion.= Outside of the abortion habit, which may be due partly to heredity or be caused by a diseased condition of the lining membrane of the uterus, the principal cause of abortion and miscarriage is syphilis. And when a woman has had two or three or four or more miscarriages in succession we generally assume the cause to be syphilis, and in most cases the assumption will be correct.