46 SPIROCILETES. 



from person to person by the bites of bugs, and it is 

 probable that at least accidental infection may thus 

 he produced, as Tictin found the spirochaete present 

 in these insects and infected monkeys by injection 

 of their macerated bodies; but it is not proved that 

 an intermediate host is necessary or that any develop- 

 ment of the spirochaete takes place in the bug. Man- 

 teufel and also Sergent and Foley believe that infection 

 is conveyed by lice (Pediculi capitis et corporis). 



The blood of a convalescent from relapsing fever 

 contains substances capable of destroying the spiro- 

 chaetes (spirillicidins) , and passive immunity is con- 

 ferred by injection of such blood into another indi- 

 vidual. Agglutinating substances are also formed. 

 Metchnikoff holds that the spirochaetes are mainly de- 

 stroyed by phagocytosis; Rabinowitsch states that a 

 hyperleucocytosis is produced in the blood of animals, 

 and also a change in the bone marrow "like leukaemia." 



Relapsing fever has been chiefly studied and described 

 as it occurs in Europe especially in Russia. Closely al- 

 lied forms of disease occur in other parts of the world, 

 caused apparently by spirochaetes which are mor- 

 phologically almost indistinguishable from that of 

 ordinary relapsing fever, but are probably different 

 species. 



AFRICAN TICK FEVER. 



African tick fever is an affection met with in East 

 Africa, and is conveyed by the bite of a species of tick, 

 Ornithodorus moubata. The general features of the 

 disease are similar to those of relapsing fever, but the 

 relapses are often more numerous. The spirochaete 

 present in this disease is said by Uhlenhuth and Haendel 

 to be rather thicker than Sp. obermeieri, and by Schel- 

 lack to move more vigorously. An attack confers 



