335 



one would be inclined to consider them quite distinct 

 did one not know their origin. 



3. Immunity. The best test of the difference 

 between two trypanosomes lies, perhaps, in the fact 

 that an animal immunized against one trypanosome 

 will yet succumb to another, e.g., Laveran and Mesnil 

 base their belief K in the non-identity of Ngana and 

 Surra on the following fact. A goat or cow recovered 

 from T. brucei infection is inoculated again with T. 

 brucei. No effect is produced, and its blood in several 

 c.c. is not infective for other animals. It is now 

 inoculated with T. evansi, and its blood becomes 

 infective even in a few drops. It cannot here be a 

 question of difference of virulence of different strains, 

 for T. brucei is as virulent as T. evansi for cattle. 

 Again, mice infected with T. equinum and cured by 

 Trypan-red or arsenic are susceptible to T. equiperdum, 

 and when cured of T. equiperdum mice are susceptible 

 to T. brucei. 



4. Preci-pitin Test.- Mayer added to the serum 

 of a dog infected with T. brucei the salt extract of 

 centrifugalised T. brucei trypanosomes. A copious 

 precipitate resulted. With the serum of a dog infected 

 with T. equinum, he got no result. 



AGGLOMERATION OF TRYPANOSOMES 



Under various conditions trypanosomes come 

 together and form rosettes, sometimes of about a 

 hundred individuals. In these the posterior ends are 

 central, united by a slimy secretion derived from the 

 blepharoplasts (?), and the flagella are peripheral. They 

 may be seen in the peritoneum after injection by this 

 path. Chemical reagents, immune sera, and also 

 normal sera, are in particular cases capable of producing 



