658 TRYPANOSOMIASIS 



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 to 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 withTr. 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, where it has wrought 

 very serious havoc amongst the native population, and the in- 

 vestigations carried on in that region have led to a knowledge 

 of its cause. The disease 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 emacia- 

 tion occurs; blood changes appear, consisting of a progressive 

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

 lymphocytosis in which the percentage of both the large and 

 small mononuclear cells is increased, so that the former may 

 constitute from 20 to 30 and the latter from 30 to 40 per cent, 

 of all the white cells present. As the disease progresses the 

 drowsiness increases till it deepens into a coma from which the 

 individual cannot be roused. Often during the disease there 

 occur irregular cedematous patches on the skin, and sometimes 

 erythematous eruptions, and effusions into the serous cavities. 

 Not every case runs a progressively advancing course. Some- 

 times along with enlargement of glands the chief early feature 

 is the occurrence from time to time of attacks of fever which 

 may be mistaken for malaria, and from these apparently com- 

 plete recovery may take place ; recurrence, however, follows as 

 a rule, and ultimately the typical terminal phenomena may 

 commence. Such cases may go on for years, and it is probable 

 that many patients die of pneumonia without exhibiting typical 



