This contains a restatement of some of von Monakow's elaborately developed theories of instincts which have been taught by him to his classes for many years. He divides the book into two parts. The first takes up the integration of the instincts and the second their disintegration. In this volume one will find the author's own philosophy and his own theories in regard to the circulation of the spinal fluid and the ectomesodermal barrier. He has incorporated some of Minkowski's own work in the development of reflexes. The illustrations and subject matter will be found to be reproduced from Monakow's various articles, but the book is of value in that his theories concerning instincts are collected in one volume.