152 INFECTION AND IMMUNITY 



population, to the action of the specific exciting cause 

 of the disease. We know that under favourable hy- 

 gienic conditions the disease has but little disposition 

 to spread, and that in the severest epidemics it finds 

 its victims almost exclusively among the destitute. 

 On the other hand, in the numerous instances in 

 which shipwrecked mariners, Arctic explorers, etc., 

 have been subjected to absolute starvation, we have 

 no account of the development of any such disease as 

 relapsing fever. Overcrowding is considered by Parry 

 to be a more potent predisposing cause than starva- 

 tion, and his careful study of the circumstances of 

 those who were taken sick during the prevalence of 

 the disease in Philadelphia (1870) seems to justify 

 this conclusion which is, moreover, supported by 

 the observations of Muirhead, Bennett, Lebert, and 

 others. 



One attack of relapsing fever does not protect the 

 individual from subsequent attacks, and second or 

 even third attacks during the same epidemic have 

 been noted. 



What has been said with reference to the factors 

 which favour the epidemic prevalence of the disease 

 will indicate the proper preventive measures. Mod- 

 ern sanitary science has, apparently, banished this 

 disease from its former haunts in European countries. 

 It has not been introduced into the United States 



