OUTDOOR EXERCISE.--Outdoor exercise is indispensable to good health. It benefits not only the muscles, but the whole body. By this means the action of the heart is strengthened, and consequently all the tissues receive a rich supply of oxygen. Exercise also promotes the digestion and the assimilation of the food. It stimulates the sweat glands to become more active; and, for that matter, the other excretory organs as well. It invigorates the muscles, strengthens the nerves, and clears the brain. There is, indeed, no part of the human machine that does not run more smoothly if its owner exercises systematically in the open air; and during normal pregnancy there is no exception to this rule. Only in extremely rare cases--those, namely, in which extraordinary precautions must be taken to prevent miscarriage--will physicians prohibit outdoor recreation and, perhaps, every other kind of exertion. Under such circumstances the good effects that most persons secure from exercise should be sought from the use of massage. The amount of exercise which the prospective mother should take cannot be stated precisely, but what can be definitely said is this-- she should stop the moment she begins to feel tired. Fatigue is only one step short of exhaustion--and, since exhaustion must always be carefully guarded against, the safest rule will be to leave off exercising at a point where one still feels capable of doing more without becoming tired. Women who have laborious household duties to perform do not require as much exercise as those who lead sedentary lives; but they do require just as much fresh air, and should make it a rule to sit quietly out of doors two or three hours every day. It will be found, furthermore, that the limit of endurance is reached more quickly toward the end of pregnancy than at the beginning; a few patients will find it necessary to stop exercise altogether for a week or two before they are delivered. Walking is the best kind of exercise, but long tramps are inadvisable during pregnancy, except for those who have previously been accustomed to them. Most women who are pregnant find that a two or three-mile walk daily is all they enjoy, and very few are inclined to indulge in six miles, which is generally accepted as the upper limit. Perhaps the best way to measure a walk is by the length of time it consumes. Accordingly, a very sensible plan is to begin with a walk just long enough not to be fatiguing and to increase it by five minutes each day until able to walk an hour without becoming overtired. It is always advisable not to crowd the exercise of a day into a single period but rather to take it in several installments, for example, an hour in the morning, and another in the afternoon. Under all circumstances, it must never be forgotten that the feeling of fatigue is a peremptory signal to stop, no matter how short the walk has been.