86 



Scientific Proceedings (36). 



was found to be infective for other monkeys on the fifth and sixth 

 days of illness. 



Diluted blood serum from a human case of tabardillo was 

 passed through a Berkefeld filter, but failed when inoculated into a 

 Macacus rhesus to cause any reaction. It would seem, therefore, 

 that either the infecting agent was too small to pass through a 

 Berkefeld filter or passed through in insufficient quantities to pro- 

 duce the disease. 



The epidemiological evidence, supported by one human exper- 

 iment, indicates very strongly that Mexican typhus fever is not 

 contagious in the usual sense of the word. An intermediary host 

 is probably the means by which the disease is transmitted from 

 person to person, and the probable insect concerned is the body 

 louse, Pediculus vestiinenti. 



The non-identity of the Mexican typhus fever and the Rocky 

 Mountain spotted fever, which prevail at approximately the same 

 altitudes, was demonstrated by animal inoculation as well as by 

 the observation of certain important clinical differences. 1 



1 Anderson, John F., and Goldberger, Joseph, On the relation of Rocky Mountain 

 spotted fever to the typhus fever of Mexico. A preliminary note. Public Heath Re- 

 ports, Dec. 10, 1909, XXIV, 1861. 



