586 The Blood Flagellates 



spleen is said to increase with rise in temperature and to decrease as 

 the temperature falls. In some cases, the disease may seem to end at this 

 stage. However, the frequency of spontaneous recovery — if it actually oc- 

 curs — is uncertain, since there are indications that the infection some- 

 times becomes latent. 



On the basis of later history, three general types have been dis- 

 tinguished (39). In a mild variety, an equilibrium seems to be established 

 with the patient in poor physical condition. In view of the lowered re- 

 sistance to other diseases, even this mild form contributes significantly 

 to depopulation. A severe acute type is characterized by marked toxemia 

 and often by oedema and may lead to death without involvement of the 

 central nervous system. The third type is the classical form with a sleep- 

 ing sickness stage. The second and third types become predominant in 

 epidemics, whereas the mild type is otherwise the most common. In 

 later stages of the third type, invasion of the central nervous system is 

 followed by sleeping sickness. This stage often develops in untreated 

 cases after a more or less prolonged period, sometimes several years. 

 Physical weakness and languor become more and more pronounced and 

 loss of weight is often striking. The patient falls asleep at irregular 

 intervals. Convulsive movements of the limbs, sometimes followed by 

 temporary paralysis, become evident. Mania may develop, and mental 

 and physical symptoms sometimes resemble those of paresis. The spells 

 of sleep gradually become more frequent, and death is usually the out- 

 come in untreated cases. 



Anemia is a common feature and becomes more marked in later stages. 

 Leucopenia, with a relative increase in mononuclears, is common, but a 

 leucocytosis may occur instead. Red corpuscles in fresh blood smears 

 may undergo agglutination at room temperature, a phenomenon attrib- 

 uted to an increase in "autoagglutinin." Swelling of the lymph glands is 

 often produced, even in early stages, by multiplication of lymphocytes in 

 the germ centers. Multiplication of cells may occur also in the endo- 

 thelium of lymph channels. Hemorrhages frequently develop, and the 

 degeneration of lymphatic tissue may be followed by invasion of fibrous 

 tissue. Enlargement of the spleen is more or less proportional to the 

 degree of anemia and to the parasitemia. Endothelial proliferation, in- 

 crease in number of phagocytes, increase in thickness of the capsule, and 

 some degeneration of splenic tissue have been observed. Endothelial 

 proliferation also has been observed in vessels of the lungs, liver and 

 kidneys, sometimes leading to obliteration of capillaries in the lungs and 

 kidneys. Lymphocytic infiltration has been noted in the heart, peri- 

 cardium, liver, digestive tract and skin. Aggregates of macrophages, 

 sometimes found in the skin, may contain ingested trypanosomes. 



The typical lesions depend upon the presence of trypanosomes in the 

 tissues. Extravascular distribution of the flagellates in experimental infec- 



