small a share his consciousness has had in the healing of a wound or a fracture; nay, the most powerful curative effects take place at the time when consciousness is as far as possible in abeyance, as in deep sleep. To which may be added, that the organic functions, so far as they are at all dependent on nerves, are regulated by sympathetic nerve-fibres, which are not directly subject to the conscious will, but are innervated by the ganglionic centres from which they spring. If, nevertheless, there reigns in the organic healing functions so wonderful a harmony tending to a single goal, this can never be explained by the material inter-communication of these different ganglia, but only by the unity of the over-ruling principle, the Unconscious.

VII.

THE INDIRECT INFLUENCE ON ORGANIC FUNCTIONS OF CONSCIOUS PSYCHICAL ACTIVITY.

1. THE INFLUENCE OF THE CONSCIOUS WILL.

(a.) Muscular Contraction.

MUSCULAR Contraction is manifestly by far the most important organic function dependent on conscious volition, for it is that whereby we move and act on the external world, through which we communicate in speech and writing. It takes place through the influence of the motor nerves, by a nerve-current flowing from centre to periphery, a current which is evidently related to the electrical and chemical streams, as we find them to be convertible, and of whose intensity we can form no mean idea when we see the contracted muscles of the athlete, attached to the long lever arms of the limbs, moreover, sporting with hundredweights, and then consider what colossal galvanic currents would be required to lift such a load with an electro-magnet. We have already seen that any muscular movement is explicable only by the repeated intervention of unconscious volition and thought, because otherwise it would not be apparent, how the motor impulse could affect the part of the nervous centre answering to this consciously represented movement rather than any other. We have further seen that the more immediate centres for most movements lie in the spinal cord and medulla oblongata, and that these movements are there so determined

and ordered that they are to be looked upon as reflexes of these centres, occasioned by the stimulus of a relatively small number of fibres proceeding from the cerebrum, so that the first motor impulse must be referred to the central endings of these fibres in the cerebral hemispheres. It may well be that several of such reflex actions take place in different nerve-centres more and more remote from the brain before a complex movement is executed, that, e.g., in walking, at first some few fibres carry the impulse over from the cerebrum, where the conscious will to walk arises, to the cerebellum (the organ which is said to coordinate the larger motor groups), that then from there a larger number of fibres carry forward the impulses to different centres of the spinal cord, and finally to the crural nerves. On occasion of every such reflexion the unconscious willing and conceiving of the specific motor instinct of the particular centre chimes in, and thus it becomes explicable how such complex movements run their course appropriately and orderly without any mental effort whatsoever. In every centre the impulse is felt as stimulus and converted into a new impulse, so that in the strictest sense we can only speak of the motor nervecurrent from the last centre.

The question now arises, how the will is able to produce the innervating current. We can only fall back on the analogies of the related and (physically) better known currents, and on the a priori suggestion, that the entire apparatus of the motor nervous system has probably been inserted in the organism with the object of making it possible for the will to produce the necessary mechanical effects with the smallest possible mechanical effort; in other words, that the motor nervous system is a mechanical power like the winds, or more truly as the wallshattering ordnance, to which the individual man has only to apply the match. To produce mechanical motion without mechanical energy is impossible, but the energy which ushers in the movement may be reduced to a

minimum, and the remaining part of the work can be handed over to forces previously stored up for use. In artillery this is the chemical energy of the powder, in the animal that of the food, which therefore must stand in the same relation to muscular energy as the quantity of powder to the force of the shot. Without some mechanical energy, however, the stored-up forces cannot be liberated from their imprisoned state; accordingly the will must, at all events, be made capable of performing mechanical work. If, however, the quantity of this energy were of no consequence, it could put the muscles into motion directly; we must therefore assume that the critical point of the motor system consists in this: How to reduce the necessary mechanical performance of the will to a minimum,-somewhat as the regulating of the levers by the engineer represents a minimum of effective energy in relation to the performances of the steam-engine. Looking now at the current which doubtless has most affinity with the nerve-currents, viz., the electrical, we must, in the first place, exclude the mode of origin by mechanical influences (as friction) or heat, because the former would be just the opposite of what we are in search of, and the latter likewise consists of vibrations with considerable mechanical oscillation of the atoms. We must in any case disregard modes of production which depend on displacement of the molecules, and keep to such as require only a rotatory motion of the same, since rotation requires infinitely less application of force than displacement. Here the results of nerve-physiology come to our aid, which show that, whilst the motor-current is traversing the nerves, all the molecules of the latter exhibit an electrical polarity in the same direction, as in the magnet, whilst in the completely indifferent state (which, it is true, does not occur during life) the polarities of the molecules have no definite arrangement, as in non-magnetic iron, and thereby neutralise one another. We learn from these experiments that the nerve-molecules possess polarity, and

that the poles, by rotation of the molecules, may be brought into the same direction. As the iron rod, surrounded by a wire, becomes magnetic as soon as a galvanic current traverses the wire, so, if in any way the iron were suddenly magnetised, a galvanic current would be called forth in the wire. In an analogous way, through rotation of the molecules, so that their polarities are turned in the same direction, is a nervous current produced.

We see in Physics that the polar oppositions of the molecules are the foundations of all the phenomena which we designate chemical, galvanic, frictional-electrical, magnetic, &c.; we have therefore no reason to doubt that many similar phenomena have the same origin, and that one of these is the nerve-current. The rotation of the molecules in the centres is thus the minimum of mechanical work, which is left to the will, and the polarity of the nerve-molecules is the reserved mechanical energy, which liberates the store of mechanical power in the muscles, which is exhausted by prolonged activity, and is again restored in repose through the chemical replacement of material. Thus every organism is comparable to a steamengine; it is, however, also at the same time stoker and engine-driver, nay, repairer also, and, we shall subsequently see, even its own fabricator.

As the mobility of the molecules is in all respects greater in the fluid state of matter than in the solid, nerves are semi-fluid; but as, when encountering an external shock, the molecules of fluids do not keep their places, but are subject to considerable displacement, nerves are not quite fluid; and hence structures, which carry on operations analogous to the nervous, are the better fitted for their work, the more they possess such a semi-fluid constitution as well as polarised molecules. Accordingly the gelatinous bodies of the lower aquatic animals, all animal germs, the plastron, the earlier embryonic conditions, the clotted neoplasm, once in a state of plastic fluidity, from which all new formations of the vis medicatrix proceed,