TRYPANOSOMA OF SLEEPING SICKNESS 661 



described by other observers. At first Castellan! was inclined 

 to look on the presence of the protozoon as accidental, but 

 Bruce, on going out with Nabarro and Greig in 1903 to pursue 

 the work of, the Commission, realised the significance of the 

 observation, urged Castellani to further inquiries, which he 

 himself continued after the departure of the latter, with the 

 result that in a series of examinations carried out in several 

 infected localities, the trypanosome was demonstrated in every 

 case of the disease. This work formed the starting-point for 

 inquiries, the results of which make it certain that the parasite 

 is the causal agent, of the condition. The organisms were not 

 demonstrable in the cerebro-spinal fluid of patients dying of 

 other diseases in the sleeping sickness area. On the other hand, 

 it was found that if cerebro-spinal fluid withdrawn from cases 

 of, the disease was injected into monkeys (especially macacus 

 rhesus), trypanosomes appeared in the blood, and in many cases 

 in three or four months the animals died of an illness indistin- 

 guishable from sleeping sickness, and with the parasites in the 

 central nervous system. It was further found that in the parts 

 round the north end of Victoria Nyanza where sleeping sickness 

 was rife, the distribution of the disease exactly corresponded 

 with the distribution of a blood-sucking insect, the glossina 

 palpalis, a species closely allied to the glossina morsitans of 

 nagana. It was found that, when one of these flies was fed on 

 a sleeping sickness patient and then allowed to bite a monkey, 

 frequently trypanosomes appeared in the animal's blood, and 

 that when fresh flies caught in the sleeping sickness area were 

 placed on a monkey a similar occurrence often took place. 



The trypanosome of sleeping sickness is 13 to 33 /x long 

 (average in man 24 '3 /A) and 1-5 to 2 '5 /A broad (Fig. 189); 

 when about to divide it grows in both length and breadth. Ac- 

 cording to Laveran, the free part of the flagellum often eauals 

 a fourth of the whole length, but occasionally the body proto- 

 plasm extends quite to the anterior end of the organism. The 

 undulating membrane is narrow, and the posterior end may be 

 either sharp or blunt. The trypanosome contains the macro- and 

 micro-nucleus characteristic of the group, and the protoplasm 

 often shows chromatin granules. It does not usually long survive 

 removal from the body, but it has been found to be motile for 

 nineteen days when kept on rabbit-blood agar at 22 C. As we 

 have said, when Tr. ugandense is inoculated in monkeys they 

 often contract an illness which ultimately presents the features 

 of typical sleeping sickness. In inoculation of other species of 

 animals, e.g., herbivora, the guinea-pig, in nearly every case a 



