38 ° 
Incubation Period. —Five to six days, the infection 
reaches a maximum in about ten days. Spirochaetes 
also occasionally occur in the blood of Mus decumanus , 
and, it is stated, in the blood of bandicoots (. Nesocia 
bandicota). 
6. Sp. muris , var. virginiana , in a wild rat in 
Virginia, 3*5 by 0*25^. Easily transmissible by inocu¬ 
lation to wild rat, the incubation period being seven 
to fourteen days. 
7. Sp. theileri. —Occurs in cattle in Africa 
(Transvaal and Cameroons). According to some the 
same spirochaete exists also in horses and sheep. 
Symptoms. —As Piroplasma sp. and P. theileri are 
also commonly present, it is difficult to ascribe the 
affection and death solely to the spirochaetes. 
Morphology. —The spirochaetes are actively motile, 
20-30/^ long. Small forms, 8/^, also occur. 
Pathogenicity. —Besides cattle, sheep are suscep¬ 
tible. 
Mode of Transmission. —The larva of the infected 
mother tick M. decoloratus (blue tick), transmits the 
disease. The incubation period from tick bite is about 
a fortnight ; and as this tick passes all its life, three to 
four weeks, on cattle, it is possible for the larval tick to 
re-infect itself when adult, from the beast it has infected 
when itself in the larval stage. 
The blood of immune animals is still infective 
( cp. P. parvum). 
8. Sp. anserina. —The cause of a fatal disease in 
geese in the Caucasus and in Tunis. 
Symptoms. —(1) Fever, (2) diarrhoea, (3) acute 
tenderness of the feet. Death occurs in about a week. 
The mortality is about eighty per cent. 
Blood Examination. —The spirochaetes occur in 
