The typhus-like disease first described under the name tropical typhus by Fletcher and Lesslar (Bull. Inst. M. Res. F. M. S., 1925, No. 2) has been the subject of the extensive investigations reported here in monographic form. Special attention has been paid to the symptomatology and Weil-Felix reaction in ninety cases of tropical typhus from the Oil Palm Estate (Selangor Province, Malaya), to the study of the experimental disease in guinea-pigs, rabbits and rats, to the bacteriologic studies and to the epidemiology of the disease, with particular reference to the rural and urban types.
The incubation period varied from eleven to twenty-one days. The disease was characterized by a rather sharp onset, a fever reaching 102 F. on the third or fourth day and increasing to 104 F. the next few days, followed by rapid defervescence, and inconstant rash which frequently attacked the face, symptoms of dysfunction of the central