TKYPANOSOMA OF SLEEPING SICKNESS 625 



of nagana. It was found that, when one of these Hies 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 sick- 

 ness area were placed on a monkey a similar occurrence took 

 place. 



The trypauosome of sleeping sickness is 17 to 28 //, long and 

 1*4 to 2 JJL broad (Fig. 172); when about to divide it is both longer 

 and broader. According to Laveran, the free part of the flagellum 

 often equals a fourth of the whole length, but occasionally the 

 body protoplasm extends quite to the 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 micronucleus characteristic of the group, and the proto- 

 plasm often shows chromatin granules. Castellaui attached great 

 importance to a vacuole often seen in the neighbourhood of the 

 inicronucleus, but, as stated above, Laveran holds this to be an 

 artefact. The organism divides longitudinally in the usual manner, 

 HI id often two can be seen to approach each other and lie more or 

 less side by side, but whether this indicates conjugation or not is 

 not known. The organism 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 into monkeys they often 

 contract an illness which ultimately presents the features of 

 typical sleeping sickness. Inoculation of other species of animals 

 is not usually so successful, though in nearly every case, e.g. in 

 the guinea-pig, a proliferation of the parasite, as indicated by its 

 appearing in the blood, takes place ; but often either no disease 

 occurs or this runs a very chronic course. The relative insuscepti- 

 bility of animals, especially of the dog, to the Tr. ugandense is 

 taken as evidence that this organism is essentially different from 

 Tr. Brucei. 



By means of microscopic examination the organisms may be 

 found in the cerebro-spinal fluid, the blood, or the juice of 

 glands. In the case of the first about 10 c.c. of the fluid is to 

 l)o ceutrifugalised for fifteen minutes and the deposit placed under 

 a cover-glass for examination ; it is better to make a little cell 

 on a slide by painting a ring of ordinary embedding paraffin, 

 t' |ilace the droplet of fluid in its centre, and to support the 

 cover-glass on the paraffin ; in this way injury to the delicate 

 structure of the organism is avoided. In fresh cerebro-spinal 

 fluid the trypanosomes can be seen to be actively motile ; the 

 number in which they occur varies very much, and the same is 

 40 



