.">M BIOLOGY OF THE PROTOZOA 



symptoms (tremors of tongue and knee, shuffling gait, etc.) which 

 characterize sleeping sickness may be due, as Reichenow (p. 582) 

 believes, to the effect of an endotoxin upon the central nervous 

 system and liberated through destruction of the parasites by lymph- 

 ocytes. Others, notably Mott, Bruce, Wolbach and Binger, Star- 

 gardt, Stevenson, et ah, interpret these characteristic symptoms as 

 due to penetration of the brain substance by trypanosomes, their 

 accumulation, with lymphocytes, in the spaces about bloodvessels 

 causing occlusion of the smaller ones with accompanying lack of 

 nourishment followed by atrophy of the brain cells. 



The Rhodesia n type of trypanosomiasis is not caused by Trypano- 

 soma gambiense but by T. rhodesiense (Stephens and Fantham), 

 which is closely related to T. brncei, the cause of nagana in cattle. 

 Like briicei, this human trypanosome is ordinarily transmitted by 

 the tsetse fly, Glossina morsitans. The disease is more rapid and more 

 severe than northern sleeping sickness. Trypanosomes may enter 

 the cerebrospinal fluid within a week after infection (Kudicke), 

 and untreated cases are usually fatal within a few months, so that 

 characteristic sleeping sickness symptoms, although they have been 

 observed, are not so pronounced as in the equatorial form of the 

 disease. 



While sleeping sickness is essentially a disease of the lymphatics, 

 Chagas' disease or Brazilian trypanosomiasis is, according to 

 Chagas, essentially a disease of the endocrine organs. The para- 

 sites (Schizotrypanum cruzi) are abundant in the peripheral blood, 

 but unlike Trypanosoma they do not reproduce in the blood. They 

 penetrate organ cells and there, like Leishmania, they divide and 

 multiply until great groups of them are present in cross-striped 

 muscles of the body, in heart muscle and in the central nervous 

 system. Such groups may develop flagella simultaneously, so that 

 in acute cases the blood may be teeming with flagellates (Reichenow). 

 Children are most susceptible to infection, and the disease is most 

 severe with them; but adults are not immune. In acute forms it 

 is prevalent in very young children, but may assume a chronic type 

 in children up to fifteen years of age, in whom it is associated with 

 retarded development of mind and body. Chagas believes it to be 

 the cause, not only of retarded development, but of functional loss 

 of endocrine glands leading to goiter, cretinism and idiocy. 



Other flagellated parasites common in man are found in the 

 intestine for the most part. These are: Embadomonas, MacKinnon 

 (1911); Chilomastix mesnili, AYenyon (1910); Tricercomonas intes- 

 tinalis, Wenyon and O'Connor (1917); Trichomonas hominis, 

 Davaine (I860); Trichomonas vaginalis, Donne (1837); Giardia 

 intestinalis , Lambl (1859). The etiological significance in each 

 case is doubtful, although the possibility is frequently admitted 

 that some of them may augment disorders of the digestive tract, 



