THE TRYPANOSOMES OF SLEEPING SICKNESS 817 



dilection for the negro race but also attacks mulattos and several cases have been 

 recorded in Europeans. 



Further observation tended to show that the Trypanosomes of Dutton 

 and of Castellani must be regarded as one and the same organism, Trypano- 

 soma gambiense (Bruce, Nabarro and Greig, Laveran). Morphologically 

 they are indistinguishable : and the difference between sleeping sickness and 

 trypanosome fever is merely a function of the localization of the same trypano- 

 some in the body. Sleeping sickness has been produced in the monkey by 

 the inoculation of Dutton's trypanosome. If the trypanosome is in the 

 blood, the disease produced is Dutton's disease, trypanosome fever ; if in the 

 cerebro-spinal fluid then the symptoms are those of sleeping sickness. [It 

 must be noted however that Nabarro states that if the trypanosome be 

 carefully looked for in sleeping sickness patients it can be found not only in 

 the cerebro-spinal fluid but also in the blood and gland juices.] Manson has 

 recorded a case in which sleeping sickness developed in an European who up 

 till that time had only shown symptoms attributed to Dutton's trypanosome. 

 Monkeys which have acquired an immunity against T. gambiense are also 

 immune against T. ugandense [and vice versa; but subsequent investigation 

 has shown that this acquired immunity is apparent rather than real and the 

 most recent work tends to show that no immunity is attainable with the 

 trypanosome of sleeping sickness (Laveran, Nabarro and others). However 

 it is now almost, if not quite, universally believed that T. gambiense and 

 T. ugandense are the same species (Nabarro)]. 



[More recent investigations have however thrown some doubt upon the 

 identity of all trypanosomes found in man. 



[Stephens and Fantham for instance have isolated a trypanosome from 

 an European who became infected in some part of North-East Rhodesia. 

 This trypanosome they regard as a new species (Trypanosoma rhodesiense) 

 and in this opinion they are supported by Laveran from his own experiments 

 and observations (see p. 820). 



[Castellani also is disposed to revert to the opinion he held in 1903 that 

 there may be more than one species of human trypanosome, possibly trans- 

 mitted by the same fly, in the same way that different species of malarial 

 parasites are transmitted by the same mosquito.] 



Methods of detection. As a general rule the blood and cerebro-spinal 

 fluid should be examined for trypanosomes and as the latter are often present 

 only in very small numbers the fluid should be centrifuged. 



Cerebro-spinal fluid. 10-15 c.c. of fluid should be withdrawn by lumbar puncture 

 (p. 199). The first few drops are rejected as they may contain a little blood and 

 this would interfere with the examination. The fluid should then be centrifuged at 

 once for a quarter of an hour and the whitish deposit used for making films, which 

 must be stained by one of the usual methods (p. 804). [It is better to examine 

 fresh unstained films as the trypanosomes obtained by centrifuging cerebro-spinal 

 fluid do not stain well.] 



Blood. When direct examination of blood films has failed to reveal the presence 

 of trypanosomes, Bruce and Nabarro collect 10 c.c. of blood in a tube containing a 

 little [1 per cent.] potassium citrate, solution, centrifuge for 10 minutes, pipette off 

 the supernatant plasma [together with some of the middle layer and a little of the 

 red corpuscle layer] and centrifuge this again. They repeat the operation four 

 times and use the deposit from the fourth centrifugation for making films for 

 microscopical examination. 



The method of Le Dantec (p. 772) may also be employed. 



To complete the identification of the organism it will also be well to inoculate 

 a little of the suspected blood or cerebro-spinal fluid into a susceptible animal 

 (for example, into the peritoneum of a rat). 



3F 



