SLEEPING SICKNESS 665 



palpalis can convey trypanosome disease set up by several 

 varieties of trypanosomes from sick to healthy animals. It 

 appears from this also, that other varieties of Glossina besides 

 palpalis can convey the Trypanosoma gambiense. These flies 

 tend to " abort " when kept in captivity. 



Experiments prove that the Trypanosoma gambiense multiplies 

 in the stomach of Glossina palpalis. It is found that infection 

 cannot be produced by inoculation of trypanosomes from the 

 intestine of the Glossina. 



The etiology of sleeping sickness has now been conclusively 

 established by the accumulation of the following facts : 



1. The death of Europeans suffering from Trypanosoma 

 gambiense infection long after they have left the country where 

 it is endemic. 



2. The production of the characteristic lesions in monkeys 

 by experimental inoculation. 



3. The absence of the lesions in any other conditions of 

 infection. 



4. The chronicity of the disease as shown by European cases. 



5. The existence of cases of sleeping sickness only when 

 Trypanosoma gambiense and Glossina palpalis coexist. 



It has been found that there is a parallelism between the 

 intensity of the lethargy, the chronicity of the disease, and the 

 characteristic histological changes in the central nervous system. 

 The disease is characterised by a chronic polyadenitis (Greig), 

 followed by a chronic inflammatory change in the lymphatics of 

 the brain and spinal cord. In practically all cases the cervical 

 lymphatic glands are enlarged, and the most chronic change 

 is found about the base of the brain. It is therefore probable 

 that the chronic inflammation of the lymphatics spreads along 

 the nerves, spinal ganglia, and nerve-roots to the central nervous 

 system, and especially along the lymphatics of the nerves and 

 vessels entering the base of the skull. The chronic inflammatory 

 change in the nervous system consists in a proliferation and 

 overgrowth of neuroglia cells, especially those related to the 

 subarachnoid space and perivascular lymph spaces of. the brain 

 and spinal cord, with accumulation, and probably also pro- 

 liferation, of lymphocytes in the meshwork. 



Preventive and Precautionary Measures. —Sleeping sickness 

 may be carried wherever an infected person travels. The 

 disease may spread wherever Glossina palpalis exists. Most of 



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