Natural historians have always insisted that it is impossible to think of a living creature apart from its environment. Indeed, the two are so intimately joined that it is no easy task to decide, for example, at what stage oxygen from the surrounding air fuses as oxyhemoglobin with the structure of the organism, or when ingested carbohydrate becomes vitalized in the energy productions of muscle. Consequently, the investigation of a human being's constitution must include all the gross and subtle details of his environment—it becomes in effect a study of the "man-environment unit." The problem would perhaps be easier if the palpable universe comprised man's only envelop. But because of his imaginative faculty, his phantasy life, another vast imponderable yet entirely personal universe supplies an equally complex and poignant environment to which he must likewise make adjustment. To the pressure of the physical world he responds in general with consciously