in every extension which it acquires; if such extension consists of a common possession, its desire and tendency to preserve such is simply explained by the fact that such possession is the ego itself. Amongst the intuited objects of the ego are to be classed also as component parts of the secondary ego of every individual, the other living individualities of the world. From the point of view of this fact, the ego appears in its social rôle. The present lectures consequently extend to the consideration of the interactions of brains in society, to culture and civilisation, and seek to establish the phenomena of these domains as facts of physical knowledge. The method of physical inquiry is that of comparison by the alteration of the attendant circumstances in which the psychical mechanism acts. Physiology bases it on experiment. Nature also supplies experiments with the results that also embrace phenomena of culture. In the directions indicated here, the diseases of the mind afford a comparative means for the investigation of the phenomena of consciousness, a doctrine of natural cerebral experiments, and a foundation for a knowledge of the phenomena of mind. μκρκ. PERIODICALS. ZEITSCHRIFT FÜR PSYCHOLOGIE UND PHYSIOLOGIE DER SINNESORGANE. CONTENTS: Vol. III. No. 5. UEBER EIN OPTISCHES PARADOXON. By _Franz Brentano_. “FLATTERNDE HERZEN.” By _Adolf Szili_. UEBER BEGRÜNDUNG EINER BLINDENPSYCHOLOGIE VON EINEM BLINDEN. By _Friedrich Hitschmann_. BEMERKUNGEN ÜBER DIE VON LIPPS UND CORNELIUS BESPROCHENE NACHBILDERSCHEINUNG. By _Otto Schwarz_. CONTENTS: Vol. III. No. 6. BEITRÄGE ZUR DIOPTRIK DES AUGES. By _M. Tscherning_. OPTISCHE STREITFRAGEN. By _Th. Lipps_. CONTENTS: Vol. IV. Nos. 1 and 2. UEBER DIE SCHÄTZUNG KLEINER ZEITGRÖSSEN. By _E Schumann_. ZUM BEGRIFF DER LOKALZEICHEN. By _C. Stumpf_. ZUR KENNTNISS DES SUCCESSIVEN KONTRASTES. By _Richard Hilbert_. LITTERATURBERICHT. The first article is on an optical paradox. Let two equal parallel lines be drawn, as in the cut below; then let two small straight lines be drawn from the extremities of these in such a way that in the first they form acute angles with the line and in the second, obtuse angles. The first, it will be seen, appears shorter than the second. What is the explanation of this phenomenon? [Illustration: Cut 1.] [Illustration: Cut 2.] [Illustration: Cut 3.] [Illustration: Cut 4.] [Illustration: Cut 5.]