There has been a great need for a psychiatric textbook written in structural rather than in purely descriptive terms for medical students and general practitioners. The usual psychiatric textbooks confine themselves to an enumeration and classification of pathological emotional states, illustrated by case material, and discussed from the point of view of differential diagnosis in terms which deal only with the psychiatric nomenclature. The effect upon the nonpsychiatrically minded reader is generally to confuse him with the intricacies of the psychiatric jargon, without adding to his understanding of the etiological factors which underlie mental disturbances, and without which the clinical entities can have little meaning for him. Why the patient fell ill of one disease rather than of another, and what significance various symptoms may have, remain as incomprehensible as before.