TRYPANOSOMA OF SLEEPING SICKNESS 661 



somes could be demonstrated in the blood, and this was usually 

 referred to as human trypanosomiasis, or trypanosoma fever, — 

 the trypanosome being named the Tr. gambiense. 



Relation of Trypanosomes to Sleeping Sickness.— Several 

 views as to the etiology of this disease had been advanced, and 

 the seriousness of the epidemic in Uganda led the Royal Society 

 of London in 1902, at the instigation of the Foreign Office, to 

 dispatch a Commission to investigate the condition on the spot. 

 Soon after, its commencing work, Castellani found in some cases in 

 the cerebro-spinal fluid, especially when this was centrifugalised, 

 living trypanosomes resembling the Tr. gambiense ; he also found 

 in- 80 per cent, of the cases post mortem a coccus previously 

 described by other observers. At first Castellani was inclined 

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

 Bruce, on going out with Nabarro and Greig in 190.3 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 it was found that if cerebro-spinal fluid withdrawn from cases 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 //. long 

 (average in man 24-3 u) and 1'5 to 2-5 /* broad (Fig. 197); 

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

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



