264 MP:M0EANDUM on TSETSIi-DISEASE. 



" ' (b) The only intermediate * host is the Tsetae-fly, in 

 which the parasite passes through a process of development 

 which has not yet been observed. 



" ' (c) After attaining its full development the parasite 

 once more enters the blood of the animals susceptible to 

 Surra, by means of the bite of the Tsetse-fly, and after an 

 interval of about four to six weeks produces noticeable 

 symptoms of disease. 



" * 2. In inoculation experiments the interval which 

 elapses until symptoms of the disease manifest themselves 

 is usually from four to six weeks. 



*"(a) Consequently at the same period parasites can 

 also be demonstrated in the blood. Analogously to malaria, 

 fresh attacks of fever always occur simultaneously with 

 the development of a new generation of the parasites, 

 while in the interval the temperature is noi-mal, and it 

 is also impossible to demonstrate the presence of the 

 parasites by means of the microscope. It is therefore 

 necessary to take samples of blood eveiy three or four 

 days, corresponding with the process of development, 

 shortly before a fresh attack of fever supervenes. 



" ' The number of the parasites, the condition of the 

 animal, and the amount of work demanded from it all 

 affect the course of the malady. When carefully tended, 

 animals suffering from Surra live for years, while great 

 bodily exertion renders the course of the disease acute. 



" ' (b) Simultaneously with the appearance of the 

 parasites in the blood careful observation also shows 

 symptoms of the disease (intermittent fever, cessation of 

 appetite, sluggishness of movements). Noticeable symptoms 

 occur only after the disease has lasted some time, in the 

 shape of emaciation and aniemia of the mucous membranes. 

 The only positive proof for the expert is and remains the 

 demonstration of the parasites in the blood. Cattle ai'e 

 more susceptible to Surra than mules. 



" ' 3. It is not permissible to regard districts rich in 

 game as being infected with Surra, since all known 

 single- and double-hoofed Ungulates succumb to the 

 disease ; neither, for the same reason, can the occurrence 

 of Tsetse-flies be associated with that of the buffalo.' 



" According to this, Veterinary-Surgeon Sclimidt 

 * Cf. p. 260, note *.— E. E. A. 



