In psychiatry general studies can lead only to the discovery of very general principles and to generalizations, the individual must be investigated for what he is—a totality—an entity, and that unlike any other one in the universe. But what are the differences between them and what are the resemblances externally and internally, chemically, morphologically and psychologically? The authors of this monograph have undertaken to review the literature and to examine into some of the problems of correlations between physical habitus and mental reaction types, and have developed a method of approach utilizing a combination of simple observation and anthropometry which would seem to enhance the value of such studies from the standpoint of clinical utilization. The review of the literature reveals numerous attempts to solve various aspects of