136 YERSIN AND VASSAL. 



Dengue is a disease that one meets with in Indo-China, sometimes 

 well characterized, sometimes hadly defined. But dengue lasts a still 

 shorter time than typhus, and the charts are in no way comparable, any 

 more than are the different symptoms. 



Among the "nonclassified tropical fevers" Manson has described one 

 which he calls "double continued fever," but this is removed from con- 

 sideration in connection with our typlms by its relapsing pyrexia; and 

 if we even regard the first attack only, the charts are in no way 

 comparable. 



IV. 



Experiments were first tried on laboratory animals. A certain number 

 of rats, guinea pigs, and rabbits received subcutaneously one or several 

 inoculations of blood taken from patients at different periods of the 

 disease. They manifested neither pathologic phenomena nor elevation 

 of temperature. We have already related our experiments on man. 



The examinations of the circulating blood as well as of specimens 

 taken by splenic puncture, which were very numerous, were always 

 negative. 



These results agree entirely with those of Galeseseo and Stalineano, in 

 the typhus epidemic of Bucharest in 1906. Besides, we verified the fact 

 as did these authors, that the terminal crisis is accompanied by a very- 

 marked and almost pathonomonic increase of mononuclear leucocytes. . 

 E. Gotsehlich, on the contrary, has described protozoa resembling P. 

 bigeminum in typhus patients at Alexandria, which he has called 

 "apiosoma." 



Our experiments prove that typhus fever is a disease in which the 

 virus is situated in the circulating blood during the second and fifth days 

 of infection. 



It is inoculable from man to man, but does not seem to affect the 

 ordinary laboratory animals. It is possible to make at least two passages 

 on man, but it must be remarked that the incubation is longer the. 

 second time than the first (fourteen and twenty-one days). 



The specific agent of typhus fever is invisible in the blood or at any 

 rate is exceedingly rare. 



These experiments, which doubtless require confirmation and elabora- 

 tion, authorize us in considering typhus fever as a disease to be classed 

 with the blood infections transmitted by the bites of insects. The trans- 

 mitting agent has yet to be discovered. Medical literature on typhus, so 

 rich in all kinds of epidemiologic documents, does not disprove this 

 hypothesis. 



V. 



The tberapeautic treatment ordinarily employed for malaria fails in 

 typhus fever. Quinine particularly is useless. We limited ourselves to 

 symptomatic medication. 



