CULTIVATION OF TRTPANO8OMB8. 681 



infected blood it is capable of transferring the disease; 

 hence, further development of the parasite in the tsetse- 

 fly is not essential for its continued infectiousness, and, 

 indeed, it is not certain that any further development 

 occurs. 



Nagana presents a remittent or intermittent type of 

 fever, catarrhal secretion from the nose and eyes, sub- 

 cutaneous edema, particularly of the abdominal region, 

 prepuce and posterior extremities, roughening and shed- 

 ding of the hair, marked emaciation, weakness and ane- 

 mia develop, and the animal dies in a state of exhaus- 

 tion. The spleen is greatly swollen, the red corpuscles 

 are diminished in number, and the urine may be blood 

 stained. The parasites are found in enormous numbers 

 in the blood. 



The disease is almost invariably fatal. It may last 

 for weeks or months in horses, and even much longer in 

 cattle. It occurs not infrequently in epidemic form, 

 wiping out the horses and cattle of infected regions. In 

 wild animals it is suggested that the disease may be 

 more chronic, and the shifting of such animals may 

 serve to introduce the infection to new regions, but only 

 to such regions as harbor the tsetse-fly. 



Novy and McNeal cultivate T. brucei on a medium Cnltivatioi 

 similar to that used for T. lewisi. The former is more 

 exacting in its conditions for growth, preferring a me- 

 dium containing blood and agar in a ratio of two to one 

 or three to one. Cultures were kept alive for at least 

 one hundred days through eight generations, although 

 virulence was soon lost. 



Trypanosoma evansi is the name given by Steele to a Surra. 

 parasite discovered by Evans (1880), in India, in the 

 blood of horses suffering from surra. It has the same 

 general morphologic features as T. brucei, with dimen- 

 sions from 1 to 3.5 or 4 microns by 20 to 35 microns, in- 

 cluding the flagellum (Musgrave and Clegg). It con- 

 tains a nucleus and possibly a contractile vacuole. The 

 whole posterior extremity is contractile, according to 

 Musgrave and Clegg, and this may also be true of other 

 trypanosomes. Its motility is moderate and eel-like. It 

 differs from the trypanosome of rats (T. lewisi) in its 

 larger diameter and in its greater pathogenicity ; T. 



