154 



MICROBES AND TOXINS 



of culture in a special medium, forms resembling spirochaetes 

 Borrel, using a different technique, has criticised the forms 

 seen by Bordet and concluded that it is not a spirochaete but a 

 new type lying perhaps between the protozoa and the bacteria, 

 and still incapable of precise definition. 



2. Cases of blood infection or septicaemias such as the 

 horse-sickness and the catarrhal malarial fever of sheep 

 (studied in particular in the Transvaal), yellow fever, cattle- 

 plague, avian-plague, and hog-cholera appear to be of the same 



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oi 



* 



FIG. 59. Various forms of the 

 microbe of bovine pleuro- 

 pneumonia according to Bordet. 



FlG. 60. Various forms of the 

 microbe of bovine pleuro- 

 pneumonia according to Borrel 

 (higher magnification than in 

 Fig. 59). 



nature. Horse-sickness and the sheep disease which resembles 

 malaria only exist in localities where there are certain definite 

 mosquitos ; like, malaria, too they were formerly called mias- 

 matic disease. Horses do not take horse-sickness even when 

 they are exposed to conditions of climate and altitude reputed 

 to be dangerous, provided they are protected from mosquitos 

 by means of wire-screens. The " heart-water " of ruminants is 

 transmitted by a tick (the bont-tick Amblyomma hebraeum). 



