624 TRYPANOSOMIASIS 



whilst about .the same time Manson reported a case of the same 

 kind in the wife of a missionary on the Congo. It thus came 

 to be recognised that in man there occurred a disease having 

 characters somewhat resembling nagana and in which trypano- 

 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. A 

 Portuguese Commission in 1902 described a diplococcus, tending 

 to grow in chains, which they isolated from the cerebro-spinal 

 fluid taken from cases during life, and to which they were 

 inclined from the constancy of its occurrence to attribute a 

 causal role. The seriousness of the epidemic in Uganda had led the 

 Royal Society of London in 1902, at the instigation of the Foreign 

 Office, to despatch a Commission to investigate the condition on 

 the spot. Soon after commencing work, Dr. 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 resembling if not identical with that observed by the 

 Portuguese Commissioners. At first Castellani was inclined to 

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

 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 practically 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 other hand, it was found that if cerebro-spinal fluid withdrawn 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 ill- 

 ness indistinguishable from sleeping sickness, and with the para- 

 sites 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 corre- 

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

 glossina palpalis, a species closely allied to the c/lossina morsitans 



