442 



TR YPA NOSOMIDM 



the virulence diminishes. The subcultures do not lose their viru- 

 lence even after the ninth passage. 



He has also cultivated in this way 5. recurrentis Lebert, 1874, 

 when the maximum growth occurs on the seventh day; 5. rossi 

 Nuttall, 1905, with a maximum on the ninth day; and 5. novyi, 

 which is the most difficult, with a maximum on the seventh day. 

 5. marchouxi has also been cultivated. Bronfenbrenner in 1914 

 simplified this method of cultivation. 



Carriers,— The Spiroschaudinnice are spread by the agency of ticks 

 and lice. 



Method of Infection, — The Spiroschaudinnice infect the ova of the 



tick, and so pass into the second generation, from which they 

 escape in the faeces and enter the wounds made by the tick when 

 it bites, and so infect the vertebrate host. Whether the same 



Fig. 130. — Granules IN AN Infected Fig. 131. — Masses of Granules in 

 Egg. Malpighian Tubule of a Young 



Unfed Nymph. (X 1,000.) 

 (From a microphotograph by Sir (From a microphotograph by Sir 

 William Leishman.) William Leisfiman.) 



method of development takes place in the louse is not known, but 

 the method of infection is thought to be due to the irritation of the 

 louse-bite causing the vertebrate host to scratch, and thus to crush 

 the louse and at the same time to cause abrasions of the host's 

 own skin. The Spiroschaudinnice, escaping from the crushed louse, 

 enter the vertebrate host through the abrasions caused by the 

 scratches. Both these are contaminative methods of infection. 

 It is believed that Spiroschaudinnia in the vertebrate can pass 

 from the mother via the placenta to the foetus, thus giving rise to 

 an hereditary method of infection, in contradistinction to the con- 

 taminative methods mentioned above. 



