1. Blood chemical examinations are of great value in the study of the early stages of mental disease especially those psychoses showing any symptoms of hallucinatory confusion. They assist in the differential diagnosis of the toxic psychoses especially of those on a uremic basis. They also aid in demonstrating the role of toxic factors in precipitating psychotic attacks in the major psychoses.2. Evidence is presented to show that manic-depressive, schizoid and confusional reactions may in their early stages be accompanied by signs of toxemia, viz., leukocytosis, acidosis, fever and nitrogen retention.3. Treatment directed toward the elimination of the toxemia is frequently effective in bringing about a mental recovery.4. The toxins, acid or otherwise, so affect the hydrated colloids of the nerve cells as to bring about a cracking of the emulsion of which the nerve cell is composed. Treatment to be effective must take place before this irreversible cracking point is reached.