TRYPANOSOMA CRUZI 629 



Trypanosoma Cruzi. Chagas, working in Brazil, observed this 

 trypanosonir in a monkey, the intermediate host being a hemipterous 

 insect of tin- genus '"//'///< //'*. As this insect also feeds on man, the 

 |ius>il.le relationship of the trypanosome to a human disease occurring 

 in that region was considered. This disease affects children, and is 

 characterised, by pronounced anaemia, the occurrence of oedema, and 

 enlargement of lymphatic glands, the spleen and liver ; it is associated 

 with a mental condition of infantilism, and ends in death with convulsions. 

 The parasite was only in one case found in the blood of infected individuals, 

 but when the blood was injected into guinea-pigs, or into callithrix 

 monkeys, a definite disease occurred, leading to death. In the peripheral 

 blood in such animals, besides free forms, an infection of the red blood 

 corpuscles witli a body resembling a malarial merozoite was seen, this 

 body apparently developing into a trypanosoma-like organism. A special 

 development of the parasite seemed to occur in the lungs, the result of 

 which was the formation of cells containing eight bodies resembling the 

 merozoite forms seen in the circulation, and analogous to what Schaudinn 

 described in the mosquito's stomach in connection with trypanosoma 

 noctua?. A cycle of development was also observed in the intestinal tube 

 of the conorhinns, and cultures were obtained on Novy and MacNeal's 

 medium. 



1 t is beyond the scope of this work to deal at length with the 

 other diseases of animals caused by trypanosomes. The chief of 

 these have been mentioned in the opening paragraph, but it may 

 be said that many others have been described in various species 

 of mammals, bin Is, and fishes, and that these are spread either 

 by flies or by leeches. The most interesting of those mentioned 

 is Dourine, a condition resembling in many ways nagana. It, 

 ho\\rver, presents this peculiarity, that infection does not take 

 place by an intermediate host, but apparently directly through 

 coitus, as it occurs only in stallions and in mares covered by 

 theea 



In several of the trypauosomal infections of animals it appears 

 as if, as in the case of Tr. Lewisi, the animal suffers little 

 inconvenience from the presence of the parasite in its blood, 

 and the view has even been put forward that with all pathogenic 

 tr\ -pa i incomes there exists a host which acts as a "reservoir" and 

 carries the organism without being affected by its presence more, 

 for example, than is the rat by Tr. Lewisi. Though no opinion 

 can be expressed on this j>oint, it is necessary to bear the fact 

 in mind that either natural or acquired immunity can exist 

 against such protozoa. Not only is this important from the 

 point of view of the investigation of the conditions under which 

 sueh tolerance fttiaea, but also from the bearing which the 

 existence of this tolerance may have on the spread in nature of 

 the parasites to a susrrptibli- -| eCMfl from immune animals which 

 still liarbiuir trypanost.mes in their blood. \Ve are, however, 



