1922] on Microscopic Parasites and their Carriers 



519 



stages become attached to another host. In addition to the piro- 

 plasmata, ticks are also responsible for the conveyance of spirochetes 

 of relapsing fever, aud in this case also the parasites pass through 

 the egg to the succeeding generation, and, even though the ticks 

 hatched from the egg never have an opportunity of taking up spiro- 

 chetes from the blood again, their offspring may also be infective. 

 In other words, the infection may pass through several generations 

 of tick. The spirochetes of relapsing fever live in the blood, and 

 though in tropical Africa, South and Central America, and some other 

 parts of the world they are transmitted by ticks, in Europe and Asia 



Fig. 9.— The Spirochete (Sxrironema recurrentis) of Relapsing Fever, 



and its development in the louse (Pedicalus vestimenti). 

 . Spirochetes as they occur in the blood of man. (Magnified 2000 times.) 



0, s Diagram of the development in the louse, showing the whole body 



invaded by the spirochetes, 

 salivary glands; o, ovum which may become infected and give rise to 

 infected larvae. 

 b, c Spirochetes in the leg and antenna, which are easily broken off, 

 so that fluid exuding from the body infects the skin. 



