not as yet been paid, and have utilized them from the stand-point of physiological interpretation.

Thus, having established the presence in the cerebral cortex of special zones of small cells subjacent to the pia-mater, and quite different in configuration from the zones of large cells occupying the deeper regions, I was led to see in this anatomical arrangement a clear relationship to a similar disposition existing in the constitution of the grey axis of the spinal cord.

As a consequence, I was led to think that if, as is experimentally demonstrated, the small elements in the spinal cord be affected by the phenomena of sensibility, it was natural to admit physiological analogies where morphological analogies exist; and consequently to consider the sub-meningeal regions of the cerebral cortex as being the histological territory specially reserved for the dissemination of sensible impressions; while the deeper zones of large cells (analogous to the anterior motor columns of the cord) might be considered as the regions of emission (psycho-motor centres) for exciting voluntary motion. Thus, I arrived at the demonstration that, in the very structure of the cerebral cortex, among the thousands of elements of which it is composed, there is an entire series of special nerve cells, intimately connected one with another, constituting perfectly. defined zones, anatomically appreciable, and serving as a common reservoir for all the diffuse sensibilities of the organism, which, as they are successively absorbed in these tissues, produce in this region of the sensorium commune that series of impressions which brings with it movement and life.

In the second part, which comprises an explanation of the uses of the different cerebral apparatuses of which the anatomical details have been previously analyzed, I have in the first place given a physiological explanation of the different fundamental properties of the nervous elements, considered as living histological units.

I have in this manner shewn that these properties, which are the ultimate generating elements of all the forms of activity of cerebral life, may be finally reduced to three principal forms :-sensibility, by virtue of which the cerebral cell enters into relation with the surrounding medium; organic phosphorescence, which confers upon it the property of storing up in itself and retaining the sensorial vibrations which have previously excited it (as we see in the inorganic world phosphorescent bodies preserve for a longer or shorter period traces of the luminous vibrations which have impinged upon them); automatism, which is merely the aptitude which the nerve-cell possesses, for reacting in presence of the surrounding medium, when once it has been impressed by this.

Having thus surveyed each of these elementary properties of the nervous elements in their origin, in their evolution throughout the organism, in their normal manifestation and pathological deviation, I arrive at the demonstration that it is by means of their combination, and by the harmonious co-ordination of all their truly specific energies, that the brain feels, remembers, and reacts; and that, in fact, being the properties in which all the others originate, they are the only living forces that are always present, always underlying the infinite series

of operations which it every moment accomplishes; and that without them that admirable and complex apparatus, at once so delicate and so simple, would be as absolutely without life and without movement, as the earth would be without the sun.

Having thus examined the elementary properties of the nervous elements, I have shewn how their cooperation may be used to explain the principal phenomena of cerebral physiology.

I have in this manner made it clear that by grouping among themselves the foregoing data, we may perceive that all manifestations of cerebral activityeven though we have to deal with the phenomena of psychical life proper, or the operations of intellectual life, like their fellows which have the spinal cord for a theatre (reflex phenomena) are always susceptible of being decomposed into three elementary phases; that they are always originally determined by the arrival of an incident sensorial impression, recent or former (phase of incidence); accelerated by the particular reaction of the interposed medium, reacting by virtue of its specific energy (intermediate phase); and completed by the secondary reaction of the intermediate medium, reacting and carrying outwards the primordial vibration which has been communicated to it (phase of reflexion).

It results, then, from this manner of looking at the phenomena of cerebral activity, that it is always a fact of the vital order which is at the origin of every process in evolution. Sensibility is always the primary motor agent; it originates all movement. Propagated through the sensori-motor machinery of the cortex, it becomes

insensibly transformed, like a force in evolution, and ends by disengaging itself from the organism in the form of a motor act.

In short, in these researches, in which my sole object has been to carry the data of contemporary physiology into the hitherto uninvaded domain of speculative psychology, I have endeavoured to show that the most complex acts of psycho-intellectual activity are all definitely resolvable, by the analysis of nervous activity, into regular processes; that they obey regular laws of evolution; that, like all their organic fellows, they are capable of being interrupted or disturbed in their manifestations by dislocations occurring in the essential structure of the organic substratum which supports them; and that, in a word, there is from this time forth a true physiology of the brain, as legitimately established, as legitimately constituted, as that of the heart, lungs, or muscular system.

As a consequence of what has just been said, it necessarily follows that this range of studies, so new and so attractive, should properly belong to the physiological physician and to him alone. Henceforward he may claim as his peculiar patrimony that special domain of the nature of man concerning which speculative philosophy has for so many centuries so long and learnedly harangued. It will be his task to fertilize it by his incessant labour, and to make it yield what all labour intelligently directed should afford, legitimate fruits— practical consequences which may be utilized for the benefit of suffering humanity. The history of medical science is present with its daily lessons, to shew us that the useful acquisitions which it has made have always been inevitably subordinated to clearer and more

precise notions concerning the anatomy of the organs whose care is its mission; and when we transfer the same aspirations to the subject which now occupies us, this fact surely authorizes us to hope that in the future we shall see new methods in the treatment of mental maladies, and modes of action more efficacious than those now at our disposal, arise from a better comprehended cerebral anatomy, and a more rationally directed cerebral physiology.

J. LUYS.