CHAPTER II 



NATURAL HISTORY OF SLEEPING SICKNESS 



I PROPOSE now to deal at greater length first with the 

 Trypanosomes and next with the Tse-tse flies, then the 

 inter-relation of the two will be considered and the relation 

 of both to the wild animals of the countries in which 

 they occur. 



Trypanosomes are not " microbes " in the accepted 

 sense of the word as commonly used ; that is, they are not 

 micro-fungi, but belong to the Protozoa, the lowest members 

 of the animal kingdom. The Protozoa can be divided 

 into four main groups, in each of which are found species 

 causing disease in man and other vertebrates. The 

 Sarcodina is exemplified by the well-known Amoeba and 

 the species known as Entomoeha, which causes dysentery. 



The next group, Mastigophora, is the one with which 

 we are most concerned at the moment, since to it belong 

 the Trypanosomes and their allies. The name, which 

 means " Whip Bearers," refers to the possession of one 

 or more lashes or Flagella, which by their rapid move- 

 ments draw or push the animal through the fluid in 

 which it lives. 



The third great group of Protozoa is the Sporozoa, which 



is only too familiar through the various species that 



cause malaria. To the last group Infusoria belong the 



myriad forms which are the delight of the amateur 



microscopist and may be seen so easily in stagnant water. 



One species, Balantidium, is a cause of dysentery. 



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