It is the purpose in this presentation to consider the nature of delirium as it is revealed through analysis of the form and content of the psychobiologic dysfunction. The form of delirium has been described by others.1In this article the content will be the primary issue, and the form will receive only preliminary consideration. The study has been made to determine to what degree content may be correlated with (1) the specific type of noxious agent and (2) the individual equipment and experience of the subject. Disorders of mental function due to a change in the brain tissue may prove permanent or may be transient with presumable restitution of the cerebrum. Disorders of the latter variety are the topic of this study. Unfortunately no single or satisfactorily inclusive term to designate this class is in general use. Adolf Meyer2proposed the term "dysergastic reaction"3for the