THE TRYPANOSOMES OF SLEEPING SICKNESS 821 



Morphology. T. rhodesiense is characterized by the fact that in the blood of 

 all sub-inoculated animals the nucleus instead of being in the middle or near 

 the middle of the trypanosome, as is usually the case, is, in some of the short 

 or stumpy forms near the posterior end more or less close to the blepharoplast 

 or even on its posterior side. Stephens and Fantham regard this morpho- 

 logical feature as in itself sufficient to distinguish T. rhodesiense from T. 

 gambiense. 



Experimental inoculation. T. rhodesiense is distinguished from T. gambiense 

 by its great virulence for the majority of animal species. 



For rats and mice T. rhodesiense invariably proves fatal whereas the viru- 

 lence of T. gambiense for these species is subject to considerable variation. 



In guinea-pigs, dogs and Macacus monkeys the duration of T. rhodesiense 

 infections is shorter than that of T. gambiense infections. 



In sheep and goats the difference in the evolution, symptomatology and 

 gravity of the two infections is quite remarkable. T. rhodesiense infections 

 lead to an acute disease with high fever, oedema and keratitis which invariably 

 proves fatal after a relatively short duration. T. gambiense infections in these 

 animals often give rise to no symptoms except fever and usually end in 

 recovery. 



Cross immunity experiments. Mesnil and Ringenbach immunized a Macacus 

 rhesus against T. gambiense and then inoculated it with T. rhodesiense. The 

 monkey died in 27 days. A control died in 10J days. 



Laveran immunized a goat and a mouse against T. gambiense ; when they 

 had acquired a solid immunity they were inoculated with T. rhodesiense. 

 They became infected like the controls. 



Laveran and Nattan-Larrier immunized a goat against T. brucei ; it became 

 infected subsequently with T. rhodesiense. 



Laveran immunized a ram and a sheep against different strains of T. brucei. 

 On inoculation with T. rhodesiense they both acquired acute infections and died. 



The converse series of experiments are difficult to effect by reason of the 

 virulence of T. rhodesiense ; but the results, so far as they go, seem to show 

 that an animal immunized against T. rhodesiense is immune to both T. 

 rhodesiense and T. gambiense. This fact according to Mesnil and Leger does 

 not invalidate the specificity of T. rhodesiense but tends to show that it is 

 closely related to T. gambiense. 



Serum reactions. Action of immune serum. A goat was infected with T. 

 rhodesiense. Twenty-two days later some of its serum was mixed with 

 T. rhodesiense and injected into a mouse. The animal survived. A mixture 

 of another portion of the same serum and T. gambiense inoculated into another 

 mouse resulted in infection (Mesnil and Ringenbach). 



Action of baboon serum. The inoculation of 1 c.c. of baboon (Papio anabis) 

 serum cured mice infected with T. rhodesiense. The same serum given in the 

 same dose had very little effect on T. gambiense (Mesnil and Ringenbach). 



Action of human serum. In doses of 1 c.c. human serum cured T. rho- 

 desiense mice in three cases out of four. On T. gambiense human serum had 

 no appreciable effect (Stephens and Fantham). 



Trypanolytic reactions. The serums of animals (man, monkeys and guinea- 

 pigs) infected with T. gambiense are trypanolytic for the homologous trypano- 

 some (T. gambiense) but have no action on the heterologous trypanosome 

 (T. rhodesiense). 



^Etiology. Both in laboratory experiments and in nature T. rhodesiense is 

 transmitted by Glossina morsitans (Kinghorn and Yorke). In Northern 

 Rhodesia about 16 per cent, of the wild game examined are infected with 

 T. rhodesiense (Kinghorn and Yorke). 



