Two Treatises∗ recently published contain the views of Professor Flechsig, of Leipzig, upon the present state of our knowledge of brain function. The first is in the form of an oration delivered in 1894 in the University Church of Leipzig, of which a new edition appeared last year. The second is a shorter pamphlet, which contains an account of the most recent researches in the structure of the brain. In the oration the notes occupy three times the space of the text; in the other treatise the notes are not so long. In both these notes are important, and form in some passages the most interesting part of the work. He holds that the time has now come when the old introspective psychology must turn for guidance to anatomy and physiology. It is only within the last few years that such claims could be entertained. The localisation of mental operations in the brain was made by Hippocrates from observations of the loss of function caused by diseases or wounds of the head. Polybos, the son-in-law of the great Greek physician, held that the brain was the centre of the nerves and the central organ of the thinking soul; and Erasistratos, of Alexandria, first taught that the superior intelligence of man depended upon the greater size of the human brain, and the more complicated structure of the convolutions. A new era began with the experiments of Fritsch and Hitzig in our own day. Since then experimental physiology and clinical observations, going hand in hand together, have led to the accumulation of a large fund of knowledge about the several functions of the nervous centres. Another path of discovery was opened by Golgi through his new method of differentiating the finer structure of the grey masses of the brain by his silver colourings; and also by Kölliker, who, working with low powers, was able to demonstrate the course of the motor and sensory nerve paths and of the association system in the brain.