Passing to fatigue of the sensory nerves, we find that a moment of over-stimulation of the second cranial nerve - say by glancing at the sun - is adequate to produce prolonged fatigue. If the stimulus is prolonged it results in permanent blindness, a not infrequent catastrophe amongst children in southern countries. Over-stimulation of the auditory apparatus for a single moment results in a deafness depending for its severity on the strength of the stimulus; while any stimulation of the olfactory nerve or of the nerve of taste renders them temporarily incapable of rightly interpreting any fresh stimulus.

So far we have dealt with nerves of special sense, and it may be claimed that these are more susceptible to fatigue than other nerves.

In ordinary life few spinal sensory nerves suffer over-stimulation from direct injury, but many know the effect of mechanical over-stimulation of the ulnar nerve, and how very slight may be the injury which leaves long and most unpleasant after-effects. When nerve fibres are thus stimulated in bulk we are readily conscious of the effect, but it is not difficult to believe that deleterious effect could be produced in a single fibre almost without affecting the consciousness of the individual.

Very slight mechanical stimulus suffices to over-stimulate unstriped muscle - be it of the arterioles or the bowel. The danger in the latter instance is known to all abdominal surgeons, who realise that the amount of paralytic ileus after operation will depend directly on the amount and severity of the manipulation to which the bowel has been subjected.

The first effect of percussion on the skin is a blanching of the part due to vaso-constriction, but this is soon followed by flushing due to vaso-dilatation. Both phenomena cannot be due to reflex in response to the same stimuli, as would be the case were we to accept the teaching that the blanching is due to stimulation of the vaso-constrictor mechanism and the flushing to that of the vaso-dilator. Were this the case the reflexes must take place together instead of one following the Other in definite and unalterable routine. Different impulses give rise to different reflexes, but it is incredible that identical stimuli should secure diametrically opposite reflexes simply as the result of repetition. The only explanation is that the blanching is due to the contraction of the unstriped muscle in the arterioles in response to mechanical stimulation, and that the subsequent dilatation is due to paralytic relaxation, which is due, in turn, to over-stimulation. It is conceivable that the phenomena might follow a pure skin-muscle reflex. If so, the reflex is one which causes constriction until the nerves of the reflex arc are so wearied by stimulation that nerve paralysis replaces the muscular paralysis, already considered as the more likely of the two possibilities. Moreover, we must remember that not only skin vessels are affected by our manipulations, but every arteriole, throughout the whole body, which may be subjected to the impulses.

On voluntary muscle fibre the effect of percussion is difficult to elucidate. It can cause it to contract only if used over reflex areas, or in the presence of certain diseases of the central nervous system or as a protective reflex. As a remedial agent, therefore, percussion has but feeble power in this respect. To hasten removal of waste products other means are more effective.

If "stimulating" massage for the moment is taken as being equivalent to "vigorous," and if we consider its action as a whole, we find that on the circulation the action is to "stimulate," but only if used very gently and very sparingly; if used to the faintest excess the action becomes inhibitory. This also applies to local heart treatment, as the heart is only a specialised blood-vessel and its muscle responds to mechanical stimulation in a precisely similar manner to other bloodvessels. On the nervous system the effect is "stimulating," but it is a stimulation that is almost inseparable from fatigue. It is therefore contra-indicated, save in its very mildest forms, if for any reason the nervous system of the part has been fatigued, or if the "tone" of the nervous system has been lowered, e.g., after severe traumatism or as part of the general deficient innervation of neurasthenia. On voluntary muscle tissue its beneficial effect is negligible, while on the unstriped muscle of the abdominal organs the "stimulating" effect is a close forerunner of fatigue.

"Stimulating" massage should therefore be applied only in carefully selected cases; it is the non-realisation of its dangers which has in certain quarters brought so many accusations upon massage as a whole. Any rapid or vigorous movement of massage which is given for its "refreshing" effect should, therefore, be administered sparingly, otherwise fatigue will follow. Massage used in this way corresponds more or less to the cold plunge or shower after exercise. If used aright it is most refreshing and invigorating; if abused the result is not infrequently disastrous. This form of "stimulating" massage finds its metier either after exercise or between the performances of different exercises.

Massage is not a panacea for all ills, but there are few conditions in which it cannot be used with benefit to the patient. Yet there are few medical men who really believe in the effect of massage, and many never utilise it at all, because when tried in a few cases they have found it fail them. The failure has been due to misuse and abuse, and both can usually be traced to one of two causes. First to the untimely and excessive administration of "stimulating" massage. Take as example the following experience: - The patient - worn out, it may be, by years of over-strain, anxiety, and physical exertion - who is at last unable mentally or physically to expend another ounce of energy, is found by the masseur totally lacking in vitality. "What is the matter here, I wonder?" says the masseur, if he is conscientious. "Doctor said it ' was just a case of nervous breakdown and that there was nothing organically wrong with him,' and yet he says he can't get up and go about his business. He just wants a thorough, good, stimulating massage all over." And he gets it! Small wonder then that the patient, whose whole illness, be it observed, is due to over-stimulation, becomes rapidly worse.