Now, to her who understands what exercises will develop each of the muscles of that arm, and who can tell at sight which are fully developed or developed at all, and which are not, it is easy to bring up the backward ones, and so secure the symmetry and the consequent general strength. The same rule holds good of all the other muscles, as well as those of the arm. Plenty of active out-door work will go far toward securing health. But it will only develop the parts brought into play, and there ought to be exercise for all. Now what daily work, and how much of it, will secure this symmetry, erectness, and strength, supposing that, at the outset, there is no organic defect, but that the woman is simply weak both in her muscular and in her vital systems? In the first place, let it be understood that the connection between these systems is intimate, and that the judicious building and strengthening of the former, and the keeping up that strength by sensible daily exercise, tells directly on the latter. Vigorous muscular exercise, properly taken, enlarges the respiration, quickens the circulation, improves the digestion, the working, in fact, of all the vital parts. Dr. Mitchell says it is the very thing also to quiet the excited nerves and brain. The amount of that exercise daily depends on the present strength of the woman. If she is weak generally, for the first fortnight the exercise, while general enough to bring all the muscles into play, must be light and easy. Then, as a little strength is gained, the work advances accordingly. If partially strong at first, invariably the first thing to do is to adapt the exercise mainly to the weaker muscles till they catch up. Suppose the right arm is stronger than the left, as frequently happens, because it has had more to do. For the first month--or, if necessary, for the first two months--let the left arm have nearly all the exercise, and that exercise as vigorous as it can comfortably take. Then, when it is found that it can lift or carry as heavy a weight, and pull or push as hard as the right, keep at it, by means of exercise, until both arms can do the same amount of work, and are equal. But suppose the arms are already equally strong, or, rather, equally weak--that both the back and chest are small; that is, not so large or well-proportioned as they should be in a well-built woman of a certain height--then all that is necessary is to select work especially adapted to strengthen the back, and other work telling directly on the chest. For the first fortnight very mild efforts should be made, and the advance should be gradual, taking great care never once to overdo it. Let the advance be made as the newly-acquired strength justifies and encourages it. What particular exercises will effect the strengthening and development of any given muscles will be pointed out in the chapter on Special Exercise, at the latter part of this book.