Hot baths in the treatment for disease is one of the oldest therapeutic procedures. The ancient Egyptians, Greeks and Romans not only used this mode of treatment, but worked out elaborate devices for its administration. The therapeutic possibilities of many of the thermal springs of Western Europe were discovered by the Romans. In this stage of the clinical application of the bath, attention was centered largely on its temperature and little on the fever produced in the patient. This situation not infrequently resulted in fatalities. Not until physiologists undertook a systematic study of the results of experimentally induced fevers was it possible to make a rational clinical application. A large mass of facts has been collected,1but little clinical use has been made of this information. Meanwhile, the importance of fever was being emphasized in another direct line of clinical investigations. Intercurrent fevers had been known since the earliest