CAUSES AND PREVENTION.--We have seen that the proportion of pregnancies which end in miscarriage is quite formidable. But this should not be true, as the accident is frequently preventable, and many of these accidents could be avoided by the cooperation of patients. As self-denial and personal inconvenience are often essential, it is only fair to explain their value. Furthermore, the, patient who appreciates the reason for certain directions the physician gives becomes responsible to herself, and is much more likely to carry them out than is one who is cautioned without receiving a satisfactory explanation. At best, however, the advice which the physician is able to offer will be imperfect, for it must not be imagined that everything is known concerning the causation and prevention of miscarriage. While our knowledge is so imperfect we must be content to make the most of what we possess. It must be added that no suggestion such as can be given here will enable anyone to dispense with her own medical adviser. On the contrary, if there is reason to fear miscarriage, the prospective mother should be encouraged to seek his counsel as early as possible. Aside from the hygienic measures which she may learn to carry out for herself, various drugs are often of great value in preventing miscarriage. Since these are not applicable to all cases, they should be employed only upon medical advice. Very early miscarriages may be explained by the loose attachment of the ovum during the first six weeks of pregnancy. This tiny, living sphere, it will be recalled, reaches the womb a few days after conception, and adheres to the uterine mucous membrane. At first, however, its roots are short and delicate, and not so capable of anchoring the ovum as they become later. It is only toward the end of the eighteenth week that the union between the womb and its contents becomes firm. From what we have learned in Chapter II regarding the anatomical conditions in the early days of pregnancy it is obvious that we need not be greatly surprised at the frequency of miscarriage. On the other hand, it must not be forgotten that there are many natural safeguards against accident: to mention only one, the uterus is ingeniously swung in the abdominal cavity so as to afford a large measure of protection against mechanical shock. Usually, the provisions nature has made are sufficient to resist forces from without which tend to dislodge the ovum. Now and then it happens that the most irrational acts will not interrupt pregnancy; indeed, they often seem particularly inert when practised intentionally.