TIIYPANOSOMA OF SLEEPING SICKNESS 621 



killed at 44 to 45 C. Novy and McNeal succeeded in cultivat- 

 ing this trypanosome also, though here it was very difficult to 

 obtain a first growth from the blood on their blood-agar medium ; 

 once >t!irtrd, however, it was kept alive through many sub- 

 cultures, the optimum temperature of growth being 25 C., and 

 it was from these sub-cultures that the infection was obtained 

 which definitely proved the organism to be the cause of the 

 disease. In cultures, as with Tr. Lewisi, short forms occur, and 

 there is sometimes a rosette formation with the flagella directed 

 outwards ; agglutination phenomena are also observable in 

 defibrinated blood. Under unfavourable conditions involution 

 forms occur, the organism dividing frequently to form round 

 flagellated individuals. 



Nearly all laboratory animals are susceptible to infection, 

 and the duration of the illness corresponds to what has been 

 observed in the natural infection of these animals. The rat has 

 been largely used for experiment and usually succumbs in about 

 ten days, there being very few symptoms up till a few hours 

 before death. A very important fact has been observed with 

 regard to this animal, namely, that individuals which have gone 

 through infection with Tr. Lewisi and which are immune are 

 still susceptible to the Tr. Brucei ; from this it has been deduced 

 that the two organisms are to be looked on as distinct species. 



Trypanosoma of Sleeping Sickness. Since the year 1800 

 the disease called sleeping sickness, sleeping dropsy, or negro 

 lethargy has been recognised as prevailing on the West Coast of 

 Africa from the Senegal to Lagos, and in the parts lying behind 

 the coast between these regions. It has also been found to be 

 rife from Cameroon to Angola and in the Congo valley, and to a 

 less extent up the Niger and its tributaries. In 1901 it began 

 to appear in the Uganda Protectorate, and it is in that region 

 that the investigations have been carried on which have led to a 

 knowledge of its cause ; here it has wrought very serious havoc 

 amongst the native population. It is characterised in the early 

 stages by a change in disposition leading to moroseness, apathy, 

 disinclination for work or exertion, and slowness of speech and 

 gait. There may be headache, indefinite pains about the body, 

 the evening temperature may be elevated several degrees, the 

 pulse tends to be soft and rapid, and in a very large number of 

 cases the superficial glands of the body are enlarged. In a 

 rapid case the lethargy becomes more pronounced ; fine tremors, 

 especially of the tongue and arms, develop ; progressive emaci- 

 ation occurs ; blood changes appear, consisting of a progressive 

 diminution of the red cells and of the haemoglobin, and of a 



