APPENDIX J. 



TYPHUS FEVER. 



UP till recently all attempts to elucidate the etiology of this dis- 

 ease by ordinary bacteriological methods have given equivocal 

 results. Certain experiments, however, performed by Nicolle 

 in 1909, during an outbreak in Tunis, are of importance. This 

 observer found that the inoculation of the monkeys, macacus 

 cynomolgus and macacus sinicus, with typhus blood gave a 

 negative result. On injecting 1 c.c. of such blood into a 

 chimpanzee, however, an illness presenting the features of the 

 disease in man, including the eruption, resulted three days later, 

 and death occurred. It was then found that the blood of this 

 animal was capable of originating a similar disease after an 

 incubation period of ten to fourteen days in the lower apes 

 referred to, and this was kept up through several passages. 

 The virulence of the material, however, gradually died out. 

 The dog and the white rat were insusceptible. It was found 

 that macacus sinicus could be infected by means of the body 

 louse, the incubation period, however, being lengthened to 

 forty days. These experiments probably throw important light 

 on the etiology of the condition, and on the means by which 

 the disease is spread in man. 



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