various reactions. These, however varied their appearances, nevertheless represent in the external world the reverberation of a former sensorial impression emanating from this external world.

Once upon their outward course, the processes of cerebral activity take two different routes, according to the variable conditions of receptivity of the cerebral medium in which they are developed, the nature of the individual, and his manner of feeling.

Thus they are sometimes reflected towards the different departments of vegetative life. They do not make their exit from the organism, and in that special sphere they produce secondary commotions of a more or less apparent kind; their reflection takes place in an entirely automatic manner, and in spite of voluntary action (return shock of mental emotions upon the physical constitution).

Sometimes, on the contrary, they appear externally, and reveal themselves by the help of various means of expression-phonetic sounds, graphic signs, appropriate gestures. The external sensorial excitation, radiating from the external world that gave it birth, is in this case directly returned to this external world.

CHAPTER I.

REFLEXION OF MOTOR PROCESSES UPON THE

PHENOMENA OF VEGETATIVE LIFE.

IN the first series of facts, when the excitations derived from the external world are not directly reflected outwards-when, under the influence of one cause or another, the primary impression remains confined within our own organism, it dies away there, and the reverberation which results extends to a greater or lesser distance. The nervous discharge of the process, arrested in its course, reacts upon one region or another of vegetative life, and this depends upon the closeness of the sympathetic links uniting each of these with the sensorium.

We have shown, on the other hand, that by reason of these connections, there exist, as it were, incessantly permeable natural channels, by which the impressions of the sensorium may at any moment become associated with the phenomena of vegetative life, and reverberate throughout the whole extent of the life of the viscera.

The result of this arrangement is that every external excitation arriving in the sensorium is sympathetically felt in the different centres of visceral life, and that the slightest excitations that wrinkle the surface of its plexuses, as well as the shocks that overwhelm it, are sympathetically propagated into such or such a depart

ment of organic life; now here and now there, centrifugal currents arise instantaneously, and carry to a distance without our knowledge or voluntary participation, prolonged reverberations of the oscillations of the psycho-intellectual sphere.

We all know what an effect painful emotions have upon the phenomena of the circulation; how the heart palpitates without our knowledge when our emotions are at work; how apt this latent over-excitement is to fatigue the vital energy, and what a serious, and long ago recognized influence mental causes have as regards the genesis of its organic lesions; how susceptible the vasomotor innervation is of becoming associated with our emotions in a similar manner; since instantaneous paralysis of the capillaries, on the one hand, is apt to determine those sudden blushes which by showing themselves upon our faces reveal so well, in spite of us, the secrets of our agitated sensibility; while, on the other hand, their spasmodic contraction excites those instantaneous pallors which as directly reflect the perturbations that traverse our sensorium.

We all know, moreover, how directly the digestive organs are associated with the impressions of this same sensorium. The stomach in particular is intimately connected with the phenomena of cerebral activity. Like the heart, it every instant experiences the return shock of our emotions, and like it, becomes the bearer of the sins of our general sensibility. Every one knows that digestion is disturbed by mental emotions; that vomiting frequently accompanies cerebral disease; and that in certain localized pains of the sensorium (hemicrania), when too strong an external excitation

evokes its sensibility, the discharge of the sensorium in erethism takes effect upon the stomach, which to some extent serves as a gate of exit for the nervous overexcitement reflected towards the organs of vegetative life.

We all know, further, how intimate is the association between the respiratory organs and our natural emotions. Sighs, spasms, anxieties, the involuntary laugh which sometimes bursts out in so unexpected a manner at the sight of a person who laughs, and the frown which shows itself under similar circumstances, are also co-ordinated external revelations that follow upon an incident excitation carried into the sensorium, and reverberated towards the organs whose business it is to carry it off externally.

More than this-and this also is a phenomenon known to us all-in certain circumstances our muscles, which are usually such faithful interpreters of our wills, escape from the regular stimulation of the conscious personality, and then, under the influence of powerful emotions, become subject to invincible excitations radiated from the sensorium, and act like treacherous servants, only in obedience to the instructions of an irregular power, and manifest, without our consent, the different states through which our inner sensibility is passing. is by reason of this substitution that our gestures, our movements, our attitudes, our physiognomy become, without our knowledge, living expressions of the different states of our sensibility, and in a manner apparent phenomena by which the phase of erethism of certain regions of the sensorium is externally discharged. In these cases our muscles of expression are

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grouped and harmonized in a co-ordinated manner, so automatically and so unconsciously that we see, for instance, those of the iris dilate and contract alternately, and express by their play, as automatic as unconscious, the different modes of sensibility of the retina which it is their business to protect.

We may say, then, in a general manner, that none of the peripheral excitations that arrive at the sensorium in the form of a vibratory impression, of a living force in activity, remain there stationary, stored up in one place. They develop there a series of secondary reactions, of energies regularly co-ordinated, which are incessantly distributed in the direction of the apparatuses of organic life, and represent the continuity of the primary movement, and, as it were, the modes of excretion of the living forces implanted in the organism, which here and there effect their physiological discharge.

Extrinsic Manifestations of Cerebral Processes. Genesis of the Will.-The processes of cerebral activity which reveal themselves externally, and make their exit from the organism in the form of voluntary conscious manifestations, must be considered successively in the two principal phases of their evolution:

I. In their period of incubation, when the process of the will is still only constituted by a purely physical impression;

2. In their second period of extrinsic manifestation, when they take form, reveal themselves in an apparent manner, and lay the purely motor regions of the nervous system under contribution.

1. In its preparatory phase of incubation, the process of the will is nothing but the riper and more advanced