APPENDIX J. 



TYPHUS FEVEE. 



All attempts to elucidate the etiology of this disease by 

 ordinary bacteriological methods had given equivocal results 

 till Nicolle initiated research on the subject in Tunis in 1909. 

 This observer found that the blood of cases of typhus fever 

 during the pre-febrile, febrile, and immediately post-febrile 

 periods was infective for both the higher and lower monkeys, 

 in the latter especially when introduced intraperitoneally. An 

 illness, frequently fatal and practically identical with the 

 disease in man (including the skin eruption), is originated, and 

 the blood of affected animals is again infective towards fresh 

 individuals. A large number of such passages were successfully 

 practised. The only other animal susceptible to similar infection 

 appears to be the guinea-pig, in which there arises an illness after 

 eight to eleven days' incubation, characterised by fever and loss 

 of weight ; the illness lasts from four to seven days and is only 

 exceptionally fatal. The virus is present in the blood during 

 the illness in the guinea-pig, and also exists in the solid organs. 

 In this animal likewise it can be maintained by passage. The 

 most important fact established by Nicolle was that infection 

 takes place through the pediculus vestimenti. Monkeys and 

 guinea-pigs can both be infected by the bites of lice previously 

 fed on a human case. There is evidence that the causal organism 

 undergoes some developmental stage in the intermediate host, 

 as the bite of the louse is specially infective from the fifth to 

 the seventh day after feeding. During the present war there 

 have been serious outbreaks of typhus fever in Serbia, Bulgaria, 

 and Poland, and sanitary measures founded on the view that 

 the body louse is essential to the spread of the epidemic have 

 met with success. It has been known that children under ten 

 years are, apparently, less susceptible to typhus than older 

 individuals, and Nicolle made the interesting observation that 

 when a family is attacked, young children, while apparently 



