148 INFECTION AND IMMUNITY 



what is known of the history and etiology of the 

 disease, and in consideration of the fact that Phila- 

 delphia is a seaport city which has constant communi- 

 cation with ports on the other side of the Atlantic, 

 which at that time were known to be infected. The 

 number of cases reported during this epidemic in 

 Philadelphia was 1 1 76. 



The coincidence of relapsing fever and typhus fever 

 has been noted in many of the epidemics which have 

 occurred in Europe, but the history of this coincid- 

 ence does not justify the supposition that there is 

 any etiological relation between these diseases other 

 than that furnished by common predisposing causes, 

 viz., the depressing effects of overcrowding, insuffi- 

 cient food, and filthy surroundings. This view is 

 supported by the fact that either disease may occur 

 alone, and the circumstance that sometimes one and 

 sometimes the other has the precedence in time 

 in those epidemics in which coincidence has been 

 observed. 



The germ of relapsing fever was discovered in 

 1873 by Obermeier, a German physician. This was 

 the first discovery of the specific germ of an infec- 

 tious disease peculiar to the human race, and opened 

 the way for the subsequent demonstration of the 

 germs of leprosy (1879), typhoid fever (1880), pneu- 

 monia (1880), tuberculosis (1882), cholera (1884), 



