TRYPANOSOMES 15 



upon animals, from its close allies T. gambiense and T. 

 bruceiy and it is now known as T. rhodesiense.^ 



In 1913 another species was found in man, causing 

 in natives of Nigeria a chronic swelling of the glands in 

 the neck very like the earliest stages of Sleeping Sickness, 

 but very rarely going beyond that ; it has been named 

 T. 7iigeriense.^ 



It must not be thought that every Trypanosome is a 

 cause of disease. This is very far from being the case ; 

 the production of disease is a mere accident from the 

 Trypanosome's point of view, an occurrence of fatal 

 import for itself as well as the host should the latter 

 die! 



Although only a few of the pathogenic species have 

 been mentioned, all of them together are a very small 

 fraction of the total number of Trypanosomes and their 

 allies that are known. They occur in the blood of fishes, 

 reptiles, amphibia, birds and,mammals ; in the vital fluids 

 of molluscs, in the alimentary canal of insects and other 

 invertebrates. 



By cultural methods it has been found that normal 

 English cattle have Trypanosomes in their blood, and 

 Bruce first found that even the species that cause disease 

 in domestic animals lives harmlessly in the indigenous 

 wild animals. Dr. Duke has shown that the " Situtunga " 

 antelope {Tragelaphus spekei) carries in its blood the 

 deadly Trypanosome gambiense without any harm to itself. 

 It must be remembered that Trypanosomes are not like 

 the bacteria such as that of anthrax, which form highly 

 resistent spores, and by the death of their host and its 

 disintegration are disseminated more widely in a condi- 

 tion in which life may be maintained indefinitely. 



The position seems to be this. Many insects, for instance 



^ Stephens and Fantham, Proc. Royal Soc, Series B, 1910, No. 561, 

 pp. 28-32. 



* J. W. Scott Macfie, Annals of Tropical Medicine and Parasitology, 

 1913, August, vol. 7, No. 3a, pp. 339-56. 



