Introduction Plan of the Research The Problem of Classification The Classification Adopted The Expressive Disorder The Receptive Disorder The Expressive-Receptive Disorder The Amnesic Disorder Cases of General Deterioration and Confusion with Aphasia Report of the Examination of an Interesting Case of Predominantly Expressive Aphasia The Regression of Symptoms Apraxia and Agnosia General Conclusions with Regard to the Control Group of Patients with Left Hemiplegia The Relation of Language and Thought Localization Summary and Conclusions INTRODUCTION Dr. Charles K. Mills, after whom this lecture is named, richly deserved this honor, for in the fifty years of his membership in the American Neurological Association his literary contributions to the scientific advancement of neurology were probably greater than those of any other member. His devotion and loyalty to the association are well shown in the fact that during his long membership he missed only one meeting. He was fortunate in that his work