THE SLEEPING SICKNESS 



177 



similarly placed in non-parasitic miscroscopic animals to 

 which trypanosoma is undoubtedly related. We find it 

 in the phosphorescent noctiluca of our seas, and in various 

 animalcules called " Flagellata." 



The creature drawn in our fig. 50 is, then, the typical 

 trypanosome. It is this which .the medical investigator 

 looks for in his human or animal patients ; it is this 

 which he has regarded as the sign and proof of infection. 

 Experiments have shown that, though so much alike in 

 appearance in the different diseases we have named, yet 

 each trypanosome has its own properties. Human blood- 



The Trypanosome (T. equiperdum) of 

 the disease called " Dourine," as seen 

 alive in the blood of a rat, eight days 

 after inoculation. 



A, the actively wriggling cork-screw- 

 like parasites ; B, the blood-corpuscles 

 of the rat. This figure, of compara- 

 tively low magnification, gives an in- 

 dication of the relative size of the 

 parasites and the blood-corpuscles. 



The blood-corpuscles are about 

 of an inch each in diameter. 



FIG. 51. 



serum is poisonous to one and not to another ; an animal 

 immune to one is not immune to another. At present 

 no treatment has been discovered which will destroy the 

 parasites when once they have effected a lodgment, or 

 act as an antidote to the poison which they produce in 

 the infected animal or man. But the fact that in some 

 cases an animal may become immune to the attack of 

 the parasite which usually is deadly to its kind, gives 

 hope of an eventual curative treatment for trypano- 

 some infection ; as does also the fact that the serum of 

 some animals acts as a poison to trypanosomes which 

 flourish in other animals. 



N 



