It has been known for a number of years that patients with syphilis, particularly those with neurosyphilis, are favorably affected by the production of a rise in body temperature. Probably the earliest investigators to use nonspecific protein therapy in syphilis were Engman and McGarry,1 who in 1916 treated a few cases of generalized early syphilis with typhoid vaccine intravenously. They noted a moderate improvement in the eruption. One conception has been that the heat alone was the main factor in producing the beneficial effect.
Cady, Engman and Elle2 recently inoculated albino rats with Trypanosoma brucei and subjected them to various degrees of heat. Briefly, the method was as follows: A Victor variofrequency diathermy apparatus was used. The rats were placed in a high frequency induction field for a period of time varying from fifteen to forty-five minutes. The body temperature (rectal) was raised from 1 to 3 degrees
ENGMAN MF, JORSTAD LH, ENGMAN MF. EXPERIMENTAL STUDY OF EARLY SYPHILIS WITH NONSPECIFIC THERAPIES. JAMA. 1931;97(21):1503-1506. doi:10.1001/jama.1931.02730210001001