This paper is the third in a series of studies made on 300 women patients with psychoses.1 As the data accumulated I was confronted with the problem of a search for causes to explain the results of normal or increased gastro-intestinal function found in many of the depressed patients. The first step led to a study of the types of human emotions; the second, to a consideration of the rôle of the vegetative or involuntary nervous system, which is intimately bound up with the endocrine glands to form the vegetative system; the third, to a brief sketch of the newer ideas in regards to the mechanism of digestive function. Finally, an attempt was made to secure as simple and sound a theoretical basis for the work as possible and to formulate in the conclusions principles that would serve to explain the results obtained. These conclusions will be found to agree