But before we consider in detail what kinds of exercise and with what accompaniment may be permitted for the muscles of the limbs, it is well that we should agree upon some method of deciding as to the quantity of such exercise. We cannot go by such measures as hours per week, for individuals vary. We must find some criterion which will guide us for each individual. The pendulum has swung in this regard from one extreme to another. Both extremes were adopted and permitted because in our guidance of girlhood we ignored facts of physiology, and, notably, because educators had not a clear conception of what it was that they desired to attain. By the consent of all who have given any attention to the subject, the great educational reformer of the nineteenth century was Herbert Spencer, and not the least of his services was his liberation of girls from the extraordinary _regimen_ of fifty years ago. There needs no excuse for a long quotation from the volume in which, just short of half a century ago, Herbert Spencer discussed this matter. Thereafter we may observe how the pendulum has swung to the other extreme:-- "To the importance of bodily exercise most people are in some degree awake. Perhaps less needs saying on this requisite of physical education than on most others; at any rate, in so far as boys are concerned. Public schools and private schools alike furnish tolerably adequate play-grounds; and there is usually a fair share of time for out-door games, and a recognition of them as needful. In this, if in no other direction, it seems admitted that the promptings of boyish instinct may advantageously be followed; and, indeed, in the modern practice of breaking the prolonged morning's and afternoon's lessons by a few minutes' open-air recreation, we see an increasing tendency to conform school-regulations to the bodily sensations of the pupils. Here, then, little need be said in the way of expostulation or suggestion.