In two previous papers one of us (Dr. Schick) and his co-workers1 observed that in certain conditions characterized by a slow pulse, notably the postfebrile stage of infections, especially pneumonia, the slow pulse might be caused by a lowered basal metabolism rather than by stimulation of the vagus nerve. It was also suggested that a low basal metabolic rate might be the cause of the bradycardia found in certain cerebral conditions, as in two cases of meningitis then reported, or in cases of tumor of the brain; similarly, that recent hepatic disease with icterus and slow pulse might be associated with a decreased basal metabolism, and it was pointed out that such studies had been neglected. A theory was then advanced to explain the low basal metabolic rate found in these conditions. Briefly reviewed, the theory is as follows: The lowered postinfectious metabolism is caused by a more or