42 



SPIROCH^ETES 



includes such diseases as syphilis, yaws, and infectious jaundice. 

 The third type is that in which occur only local ulcerating sores 

 of skin or mucous membrane; of such a nature are the other 

 diseases named above. 



Relapsing Fever 



In every continent in the world, with the possible exception of 

 Australia, there occurs a form of relapsing fever caused by spiro- 

 chsetes in the blood. In Africa it ranks next to malaria and 

 sleeping sickness as a scourge of that disease-cursed country. 

 In India it is hardly less severe, while in Eastern Europe and 

 America it is a mild disease. The clinical effects of these various 

 strains of the disease vary, especially in the number and duration 

 of the relapses. The mode of transmission also varies and the 

 parasites are apparently distinguishable and are therefore given 

 different scientific names. The African spirochaete, Spirochceta 



duttoni (Fig. 6), is the largest, 

 being about 16 /* GrW of an 

 inch) in length ; it has only two 

 or three complete spiral turns 

 and is quite generally admitted 

 to constitute a distinct species. 

 The other forms, Sp.recurrentis 

 of Europe, Sp. novyi (Fig. 5B) 

 of America, Sp. carteri of ori- 

 ental countries, and perhaps 

 still others in other regions, 

 are often looked upon as mere 

 strains or varieties of Sp. re- 



Spirochceta duttoni in blood of currentis, which was the one 



first described. These so- 

 called species differ among 

 themselves chiefly in size, and 

 in the closeness and regularity of the coils. Each type, however, 

 is quite variable within itself, and one is likely to be misled as 

 to size by the hanging together of several individual or partially 

 divided spirochsetes in a chain. The varying symptoms of the 

 different types of the disease and the fact that immunity to one 

 does not give immunity to another are reasons for considering the 

 relapsing fever spirochaetes as constituting several species. 



FIG. 6. 



experimentally infected rat. Upper indi- 

 vidual shows transverse fission. X 1000. 

 (After Novy and Knapp.) 



