The fourth principle is to graduate activity so that, when one feat has been successfully accomplished, a second shall be devised which, in its performance, will entail an almost imperceptible, but none the less real, increased expenditure of energy. The simplest and best way is to compel the force of gravity to serve our ends, and this is merely a question of postural treatment in the early stages. For instance, the effort exerted by the long extensors of the wrist in performing dorsi-flexion while the forearm is in full supination is negative. As it passes the mid-position between pronation and supination the zero point is reached and passed, whereas in full pronation the muscles have to work against the full force of gravity.

In our present state of knowledge it is unfortunately impossible for us always to comply with the fifth principle in muscle training, namely, always to select as the first movement in training the one action which, in normal life, represents the sole and true function of the muscle. The science of "myology," as MacKenzie calls it, is still in its infancy. He claims that each muscle has one action and only one, and that it cannot perform this action unless the antagonist is relaxed. These claims seem to me to be exaggerated, and I prefer to believe that a muscle has one definite or primary action, but that it may have various subsidiary actions.1 Thus, when we perform a certain movement, it seems quite possible that this particular effort is performed in the main by some one muscle whilst others may give subsidiary aid and act as synergists. When performing some other movement, one of these may assume the primary role while the first adopts that of synergist. The subject of synergistic action is terribly involved. A mere glance at a lower limb, for instance, suffices to show that the gluteus maximus, the quadriceps and the calf muscles are synergistic in maintaining the upright attitude. Then, too, there is no doubt that the dorsi-flexors of the wrist are the most powerful synergists1 of the long flexors of the fingers, and little question that the radial extensors act as synergists to the abductor minimi digiti. That this synergistic action is a definite reality is shown in all cases of peripheral nerve injury. If a single muscle group is paralysed, and the motor cortex orders the movement to be performed which is usually the function of this group, the paralysed group fails to respond. But, the muscle not being represented on the cortex and only the movement, contraction of other muscle groups invariably takes place, with the not infrequent result that extension will follow the demand for flexion and vice versa. Any severe straining to cause the paralysed muscle to act will invariably cause contraction in unparalysed groups, and the greater the strain the more widespread becomes this contraction till, perhaps, every muscle in the limb and even in its unaffected fellow will pass into contraction.

1 See footnote, p. 238.

As has been mentioned already, the statement that, when a muscle contracts, its antagonist relaxes is only a partial truth. For instance, it is perfectly possible voluntarily to contract the brachialis anticus without causing flexion of the elbow by merely, at the same time, contracting the triceps with equal force. If the strength of the contraction of the triceps relaxes, flexion takes place; but the relaxation of the triceps is not as a rule complete. It partakes far more of the nature of voluntarily graduated relaxation, volition controlling it so that freedom of action of the brachialis is controlled. In fact it seems probable that, in ordinary life, stability and co-ordination in movement are dependent on simultaneous action of both the prime mover, as Prof. Wood-Jones calls it, and its antagonist, co-ordinated movement being dependent upon the simultaneous voluntary contraction of the one and relaxation of the other. Once more, then, we see the vital importance of training voluntary relaxation before, or at least simultaneously with, voluntary contraction.

The fifth principle is therefore by no means easy to put into effect, but MacKenzie has shown us clearly the movements in which each muscle or muscle group acts as a primary agent, and this is the first movement we must encourage it to perform. The sixth principle entails a personal element in training that can only be developed with experience. It consists of the blending of rest with activity. Few things are more inimical to success than fatigue. Sub-maximal effort may, and should, be repeated frequently and at constant intervals through the day, four to six times according to the state of recovery. Maximal effort should be performed but seldom, once only on each occasion at most. This does not mean that progress will necessarily be slow, for the maximal effort of to-day should (and will, if training and response to training are efficient) be sub-maximal to-morrow. It will only be so, however, if the patient plays his part. It should be the first duty of every masseur to explain this to his patient. The most skilful training is void of effect without the obedient co-operation of the patient between the times fixed for definite training. Unless the patient realises this he is apt to rely on his masseur to cure him. This is impossible: there is only one person in the world who can do this, and that is the patient himself, and his curative agent is volitional effort. This he must be made to realise from the outset. What, then, is the part of the masseur? Surely this: he must guide volitional effort to success, realising that unguided effort, however persevering, will either fail to attain success at all, or will do so far more slowly than when efficient aid is given. The guidance is needed in two directions. The patient must be taught what not to do, no less than what he must do. He must also be taught how much he may do and how often he is to do it. He must be shown faults, he must be checked if too eager, encouraged if too slack; and these things are fully enough, and more, to satiate the most enthusiastic masseur. Few, indeed, can undertake any great amount of this type of work. Not only is intimate (and unusual) knowledge required; the close attention to minutice is mentally exhausting. If it is not so, we may be sure that the work done is inefficient. It is pitiable, moreover, at the end of a long day to see a masseur giving mere massage - a quite useless performance it may well be - to a patient, because he is too mentally tired to give the only treatment that is of any avail, namely, muscle training.