726 INFECTION AND IMMUNITY. 



to fasten itself in such localities and does not ex- 

 tend with rapidity to neighboring communities in 

 which good hygiene and cleanliness prevail; it is 

 particularly a disease of the poor, the filthy and 

 the underfed. Healthy, clean and well-nour- 

 ished persons who enter an infected district and 

 come in contact with the patients are subject to 

 attack. Typhus has always been considered a very 

 contagious disease. It has been noted repeatedly, 

 however, that when patients are removed to a hos- 

 pital and kept under clean and hygienic conditions 

 with plenty of fresh air that infection of attend- 

 ants and physicians is relatively infrequent. 



Mexican typhus, or tabardilli, resembles Euro- 

 pean typhus closely, but lias a longer incubation 

 period and reaches the crisis a few days before 

 the European typhus does. There is less tendency 

 to confluent eruption and hemorrhage. 



Nicolle and his associates were able to produce 

 typhus in the chimpanzee by the injection of 

 blood from European typhus patients and in a 

 similar way in the Macacus monkey with blood 

 from infected chimpanzees. Direct transmission 

 from man to the macacus was not accomplished. 

 Anderson and Goldberger were able to transmit 

 tabardillo directly to the monkey by inoculations 

 with the blood of typhus patients. Their results 

 were confirmed by Bicketts and Wilder, who deter- 

 mined the following points: "1. Macacus rhesis 

 can be infected with tabardillo invariably by the 

 injection of virulent blood from man taken on 

 the eighth to tenth day of fever. 2. Attempts to 

 maintain typhus in the monkey by passage through 

 other monkevs were unsuccessful. 3. Monkevs 



