662 SCIENCE PROGRESS 



Persians is absent. In some districts sleeping sickness and 

 Filaria perstans are both present ; but the latter is found in the 

 blood of the healthy as well as in that of the sick. 



The report of Lieut.-Col. Bruce appears to show conclusively 

 the following facts : 



i. Sleeping sickness is caused by the presence in the blood 

 of a trypanosoma. 



2. This species is probably the Trypanosoma gambiense. 



3. The cases of trypanosoma fever, described as occurring 

 on the west coast of Africa, are probably early cases of sleeping 

 sickness. 



4. Monkeys are susceptible to sleeping sickness, and show 

 the same symptoms, whether the trypanosomes injected are 

 derived from cases of trypanosoma fever or from the cerebro- 

 spinal fluid of cases of sleeping sickness. 



5. Dogs and rats are partially susceptible, but guinea-pigs, 

 donkeys, oxen, goats and sheep are absolutely refractory. 



6. Trypanosomes are transmitted from the sick to the 

 healthy by a species of tsetse fly, the Glossina palpalis, and 

 by this only. 1 



7. The distribution of sleeping sickness and that of Glossina 

 palpalis correspond. 



8. Sleeping sickness is a human tsetse fly disease. 



The discovery of the trypanosome by Dr. Castellani was due 

 to his introduction of the method of centrifuging the cerebro- 

 spinal fluid. It has been found that the cerebro-spinal fluid 

 in every case of sleeping sickness taken by lumbar puncture 

 during life contains trypanosomes. The cerebro-spinal fluid 

 taken by lumbar puncture during life from cases other than 

 those of sleeping sickness does not contain trypanosomes. In 

 the blood in cases of sleeping sickness trypanosomes are also 

 invariably found to be present. 



There is evidence to show that trypanosome fever is merely 

 the first stage of sleeping sickness, corresponding to the period 

 during which the trypanosomes are in the blood only, and have 

 not gained entrance into the cerebro-spinal fluid. No difference 

 can be found microscopically between the trypanosome of 

 trypanosome fever and that of sleeping sickness. It is found 

 that the tsetse flies of East Africa are capable of conveying the 



1 Further evidence, as will be mentioned later, seems to show that other species 

 of Glossina may convey the disease. 



