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 WILHELM WUNDT, Grundziige d. Physiologischen Psychologie. 241 Grundzilge der Physiologischen Psychologie. Von WILHELM WUNDT. Fiinfte vollig umgearbeitete Auflage. Leipzig : Engelmann, 1903. Translation of Part I. of the same by E. B. TITCHENER. Sonnenschein, 1904. THE fifth edition of Prof. Wundt's great work fills more than two thousand pages and treats of so large a mass of controversial mat- ter that the call to review it has produced a temporary mental paralysis, and this, my excuse for the tardy appearance of this notice, is offered together with humble apologies to the readers of MIND. It is not necessary to dwell on the merits of the work or to point out again that it marks an epoch in the- history of psy- chology, and, since it is impossible to deal with all its many as- pects, I propose to select one only for criticism, to inquire how far Wundt's handling of the physiological data, so rapidly added to since the appearance of the first edition, is satisfactory, how far he succeeds, by bringing them into a natural and helpful relation to the psychological data, in laying the foundation of physiological psychology, in short to examine his treatment of the principal psycho-physical problems. The greater part of the first volume is devoted to an exposition of the structure and functions of the nervous system. The doctrine set forth represents a well-defined stage in the development of neurological science. Tt has long been known that the central nervous system seems to be wholly made up of fibres and nucleated cells. The fibres seem to be of the same nature as those which constitute the peripheral nerves. In the latter they seem to play the part of excitable conductors of the nervous impulse only, and the most refined methods of research have revealed no important differences of structure or function among them. Therefore, when the doctrine of the punctual seat of the soul was found to be un- tenable and a more materialistic view of the nature of mental processes began to predominate, it became usual to regard the nerve-cells of the central nervous system as the seats of processes very much more complex than those of the fibres, and to speak of a single cell as the seat of a percept or idea, or of the processes which are the physical correlates of such a complex state of con- sciousness. This view is still maintained by some authorities, but by most it has been given up in favour of the conduction-hypo- thesis, the view that the central nervous system consists essentially of a vast system of conduction-paths whose function is to distribute in an orderly fashion to the nerves leading to the executive organs the impulses initiated in its various parts, either spontaneously or by the arrival of impulses along the sensory nerves. This orderly distribution or co-ordination of efferent impulses seemed to be the expression of the existence of paths of very various degrees of openness or resistance through the vast network which the fibres of the central nervous system were supposed to constitute. Later it became clear that the co-ordination of impulses effected by the