Exercise is essentially important to the health of the infant. Its first exercise, of course, will be in the nurse's arms. After a month or two, when it begins to sleep less during the day, it will delight to roll and kick about on the sofa: it will thus use its limbs freely; and this, with carrying out into the open air, is all the exercise it requires at this period.

When the child has acquired sufficient strength to take active exercise, he can scarcely be too much in the open air; the more he is habituated to this, the more capable will he be of bearing the vicissitudes of the climate. Children, too, should always be allowed to amuse themselves at pleasure, for they will generally take that kind and degree of exercise which is best calculated to promote the growth and development of the body. In the unrestrained indulgence of their youthful sports, every muscle of the body comes in for its share of active exercise; and free growth, vigour, and health are the result.

If, however, a child is delicate and strumous, and too feeble to take sufficient exercise on foot, and to such a constitution the respiration of a pure air and exercise are indispensable for the improvement of health, and without them all other efforts will fail, riding on a donkey or pony forms the best substitute. This kind of exercise will always be found of infinite service to delicate children; it amuses the mind, and exercises the muscles of the whole body, and yet in so gentle a manner as to induce little fatigue.

The exercises of horseback, however, are most particularly useful where there is a tendency in the constitution to pulmonary consumption, either from hereditary or accidental causes. It is here beneficial, as well through its influence on the general health, as more directly on the lungs themselves. There can be no doubt that the lungs, like the muscles of the body, acquire power and health of function by exercise. Now during a ride this is obtained, and without much fatigue to the body.

The free and equable expansion of the lungs by full inspiration, necessarily takes place; this maintains their healthy structure, by keeping all the air-passages open and previous; it prevents congestion in the pulmonary circulation, and at the same time provides more completely for the necessary chemical action on the blood, by changing, at each act of respiration, a sufficient proportion of the whole air contained in the lungs, all objects of great importance, and all capable of being promoted, more or less, by the means in question.