38 SOME MINUTE ANIMAL PARASITES 



differentiate them from ordinary T. gambiense. But, 

 in addition, a well-marked and very important feature 

 was that about 6 per cent, of the parasites had the 

 nucleus posterior (Fig. 7, A-D) and not in the usual 

 central position. These trypanosomes with posterior 

 nuclei were stout and stumpy (Fig. 7, D). Because 

 of both its extraordinary virulence and its structural 

 differences, the parasite must be considered as a new 

 species, and consequently it was named Trypanosoma 

 rhodesiense, after the country in which it was first 

 reported. A further reason for the creation of a new 

 species was that, so far as could possibly be ascer- 

 tained, the patient had never been in a district where 

 G. palpalis, the transmitter of T. gambiense, was 

 known to occur. However, the man had frequently 

 been exposed to the bites of G. morsitans, and in one 

 district through which he had passed, G. fusca was 

 present. Consequently the inference was forced 

 upon the investigators that a new carrier of the new 

 parasite had been working, and that T. rhodesiense 

 had been transmitted either by G. fusca, or more 

 probably by G. morsitans. Next a cable stated that 

 Dr. Kinghorn had just proved the accuracy of the 

 inference of Stephens and Fantham by transmitting 

 T. rhodesiense by G. morsitans. Two additional 

 reasons for the creation of T. rhodesiense have been 

 afforded by a biometric study of the parasite and by 

 cross-immunity experiments, both of which show 

 difference from T. gambiense. 



Since this first case of T. rhodesiense, other cases 

 from Rhodesia have been reported, and also victims 

 have been found in Nyasaland, The life-history of 



