One who has seen Rocky Mountain spotted fever cannot fail to be impressed with certain points of similarity which the disease shows to typhus fever (typhus exanthematicus), basing the comparison on the descriptions of typhus which are given in standard treatises. These descriptions refer to typhus as it occurs in certain European and Asiatic countries. It seemed desirable, therefore, to study their relationship, along clinical, anatomical and immunological lines, at least in certain essential respects.
Our observations concern tabardillo, the typhus fever of the great Mexican plateau, which differs in some important respects from European typhus, according to the opinion of those who have studied the disease minutely (e. g., Jose Terres, in ``Etiologia del Tabardillo''). It is stated that the typhus of Mexico has a more gradual onset and defervescence than that of the old world. These are both said to be very sudden in the latter, whereas in