TYPHUS FEVER 545 



Nicolle and Conseil have found it possible directly to infect 

 the Macacus sinicus and rhesus monkeys from human 

 cases. 



Nicolle ascertained that the blood is virulent from the 

 commencement of infection and continues so until the 

 day after the temperature becomes normal. The dog and 

 rat are quite refractory. The disease appears to be trans- 

 mitted by the body-louse (P. vestimenti), not by the flea, 

 as suggested by Matthew Hay. 



The blood from a mild case does not produce immunity 

 on injection, nor does a mild attack itself induce any 

 appreciable immunity. On the other hand a severe 

 infection induces considerable immunity. Nicolle and 

 Jseggy have not detected any microbe in affected persons 

 or animals. As the polymorphonuclear leucocytes suffer 

 considerably during the attack, undergoing fragmentation 

 of the nucleus and necrosis, it is suggested that the micro- 

 organism may be intra-leucocytic. 



Other researches have been carried out in America on 

 the typhus of Mexico, known locally as " Tabardillo." 

 Anderson and Goldberger first showed that the Macacus 

 rhesus monkey could be directly infected with Mexican 

 typhus. Ricketts and Wilder have confirmed this, and 

 find that typhus blood is not infective if passed through a 

 Berkefeld filter, indicating that the micro-organism is of 

 appreciable size. They also find that the disease is con- 

 veyed by the body-louse, and, moreover, that the infection 

 is hereditary in the louse, the second generation of lice 

 derived from infected lice apparently being still infective. 

 Neither bugs nor fleas conveyed the disease. 



In the blood of typhus patients Ricketts and Wilder 

 detected a small bacillus, measuring 2 /UL in length by O6 yu, 

 in breadth, tending to stain at the poles and belonging to 

 the group of the hsemorrhagic septicsemic bacteria. It is 

 cot numerous, and is found from the seventh to the twelfth 



35 



