Page:Popular Science Monthly Volume 33.djvu/347

Rh is in its turn divided into two parts, accordingly as it studies the sound man or the diseased man. The former is physiological psychology properly called, the other pathological psychology. This distinction is, however, more ideal than real, because so far the whole study has proceeded rather by the pathological road than by the direct observation of the healthy condition; but it is, nevertheless, correct in principle.

The matter of the new science comprises a number of facts not yet connected or co-ordinated, but which have been determined, to a certain extent. Among them are cerebral localizations, aphasia in particular, the muscular sense, heredity, suggestion, double consciousness, etc., besides others which have been longer known.

The theory of cerebral localizations was suggested by Dr. Gall and the phrenological school, who, however, compromised it by associating it with an untenable system, for which they did not offer a shadow of positive proof. Flourens approached the subject in a scientific manner, with experiments on the brains of pigeons, from which he deduced that the brain participates in the functions of thought and feeling as a single whole. He nevertheless opened the way to localizations by distinguishing various organs in the brain, and employing the distinctions of the spiritual philosophy between sensation and thought, seating the latter in the brain and the former in the spinal marrow. The theory of localizations has become much more precise since Flourens. Not only has it been possible to seat the motor functions and their various disorders with a quite novel precision in their several parts of the brain and spinal cord, but the mental faculties also have begun to yield to efforts to localize them. Thus, the faculties of pure thought have been placed in the gray matter, and the plurality of the cerebral organs and the diversity of their functions appear to have been established in the surest and most brilliant manner in the theory of the seats of language, in which the faculties relating to speech, reading, writing, and hearing are severally assigned their specific quarters. In this we have one of the clearest and most precise of the data of psycho-physiological science. The object of this science is the determination of the physiological or organic conditions of the mental faculties. In the present case the mental faculty is language; the plurality of seats is the organic condition; and this plurality explains the singular separations that are made in certain morbid cases between groups of phenomena absolutely homogeneous, as, for example, between reading and writing. Yet it is doubtful if we can go on to say that this explains language itself in so far as it is a psychological faculty. It is a case of cerebral topography and correlation, but nothing more.

One of the most obscure and complicated questions of