500 FAMILY: TRYPANOSOMID^ 



forms described under the various names mentioned above belong to this 

 species. The trypanosomes are never very numerous in the blood of 

 adult cattle, and it is highly probable that the variations in size on which 

 the different species are based merely indicate different developmental 

 stages. By injecting the forms which were named T. transvaaliense by 

 Laveran into an ox, Theiler, according to Laveran and Mesnil (1912), 

 produced an infection showing the typical T. theileri forms. Similar 

 results were obtained by Behn (1910a) in Germany. By inoculating 

 calves with the blood of a cow in which trypanosomes had been demon- 

 strated by the cultural method, a comparatively large infection was pro- 

 duced. At first the trypanosomes were small and numerous, but after 

 five days they became scanty and assumed the large form characteristic 

 of T. theileri. 



T. theileri var. somalensis, described from cattle in Somaliland by 

 Croveri (1920), does not differ in any essential respects from T. theileri. 

 It is commonly seen in animals used for the preparation of rinderpest 

 serum, and is said to become pathogenic during the course of this disease. 



T. theileri has frequently been demonstrated in the blood of cattle by 

 the cultural method when direct blood examination has been negative. 

 The first experience of this kind was that of Miyajima (1907), who was 

 attempting to cultivate a cattle piroplasm in Japan. In the cultures 

 flagellates appeared, and he supposed he had demonstrated a flagellate 

 stage in the development of the piroplasm. Miyajima's experiments were 

 repeated by Martini (1909) in the Philippines. He was able to demon- 

 strate that the flagellates had no connection with the piroplasm. These 

 results were confirmed by various observers in Europe, Africa, and America, 

 and it was shown that the flagellates in the cultures were derived from 

 T. theileri, which was present in very small numbers in the blood. The 

 culture is made by abstracting sterile blood from the jugular vein, and 

 adding it to twice its volume of ordinary nutrient bouillon. The mixture 

 is kept at a temperature of about 25° C, and flagellates of various forms 

 begin to appear towards the end of a week, and attain their maximum in 

 a fortnight. Subculture may be carried out in the same medium or in 

 blood-agar media. In the cultures every variety of form between small 

 round bodies of the leishmania type having a diameter of 2 to 3 microns 

 up to large crithidia forms occur. The largest forms Avhich may have the 

 trypanosome structure are 60 to 70 microns in length, and resemble T. thei- 

 leri as seen in the blood. Herds of cattle examined by the culture method 

 have shown a percentage of infected individuals varying from 10 to 70 per 

 cent. As far as is known, the infections in no way inconvenience the host. 



Theiler (1903) claims to have transmitted the trypanosome through the 

 agency of Hippobosca rvfjies and H. wacidata. Flies fed on infected 



