378 



susceptible to inoculation with S. duttoni, and vice 

 versa. 



Pathology. In animals the chief change is in the 

 spleen, which is much enlarged, with haemorrhagic 

 infarcts and areas of necrosis in chronic cases. There 

 may be effusion into the serous cavities, and petechiae 

 of the membranes. Necrotic areas occur in the liver, 

 and the lymphatic glands are often haemorrhagic. 

 The bone marrow is soft. 



Mode of Transmission. This is effected by Ornitho- 

 dorus moubata (p. 329) in the adult and nymphal stage, 

 the latter being probably by far the most important. 

 The transmission is thus hereditary. The incubation 

 period from tick bites, in the case of animals, is about 

 five days. Koch found from seven to fifty per cent, of 

 ticks collected from native huts, infected. Koch found 

 spirochaetes in about twenty-five per cent, of eggs up 

 to the twentieth day of development in the ovaries 

 of ticks which .had sucked spirochaete blood. 



ADDENDUM 



The spirochaete in East African tick fever is 

 morphologically identical but different from S. duttoni, 

 according to Fnenkel. 



3 . Sp. novyi. Uhlenhuth and Haendel have shewn, 

 by means of agglutination with specific spirochaete sera, 

 that the American relapsing fever is different from others. 



It is about 17/4 long by 0*3^ broad, the undulations, 

 six to eight in number, 1*9^ in width. 



4. Sp. carteri (Mackie) of Bombay relapsing 

 fever, the mortality of which is 38 per cent. The 

 commonest forms-.are 10 to 16^, average length 26 to 

 32^ by o*S/^. Monkeys are the most susceptible, but 

 according to Mackie other animals can also be infected 

 at least temporarily. 



