358 The Animal Kingdom 



and are transmitted from one host to another by some arthropod. Some 

 forms are quite harmless to their hosts while others are almost always 

 fatal. One comparatively harmless form is that known as Trypanosoma 

 lewisi which occurs in rats, and is spread by the fleas which live on 

 the rat's fur. In Africa, two species, T. gamhiense and T. rhodesiense, 

 are responsible for the two forms of African sleeping sickness. These 



Fig. 113. — Various species of flagellates. A, Trichomonas sp.; B. Giardia sp.; 

 C, Trichonympha sp. from intestine of termite; D, Trypanosoma sp. with two red 

 blood cells; E, Ceratium sp., a dinoflagellate; F, Noctiluca sp., a dinoflagellate; G, 

 Peranema sp., a free-living species; H, Gymnodinium sp., a dinoflagellate. 



are transmitted by the bite of the tsetse fly. These trypanosomes in- 

 vade the nervous system. At first the disease is characterized by fever 

 and swelling of glands in the neck region. Gradually the infected in- 

 dividual becomes more lerfiargic, and finally coma culminating in death 

 ensues. Recently progress has been made in developing drugs, which 

 effectively combat this disease. It may be transmitted from man to 

 man or from man to various wild beasts who thus act as reservoirs 

 for this devasting disease which has made whole sections of Africa 

 uninhabitable. 



