84 THE ANIMAL PARASITES OF MAN 



inhabitants. The bite is somewhat painful. The disease has since 

 been found in other parts of Brazil, e.g., Matta de Sao Joao in Bahia 

 province, Goyaz, Matto Grosso and Sao Paulo provinces, as \vell as 

 in Minas Geraes. 



Morphology. The trypanosome has a large blepharoplast or kinetic 

 nucleus. It is stated to occur both free and in the red blood corpuscles 

 in the peripheral blood. It is about 20 fj, long, on an average. 



Two forms of the parasite (fig. 33, 6, 7) are described in the human 

 blood. In one free form there is a large egg-shaped blepharoplast 

 and the posterior (aflagellar) end of the parasite is drawn out. The 

 blepharoplast (kinetic nucleus) may have a chromatin appendage. 

 The nucleus is oval or band-like, containing a karyosome. The 

 flagellum, starting close to the blepharoplast or its appendage, has a 

 free portion of variable length. The other free form in the blood has 

 a more or less round, terminal blepharoplast, smaller than in the first 

 form, without a chromatin appendage as a rule. The body of this 

 second form is decidedly broader than that of the first mentioned. 



FIG. 33. 7 rypanosoma cruzi. Schizogony. j, merozoite in red blood corpuscle ; 2, 

 parasite totally enclosed in red cell, no flagellum or undulating membrane; j-j, parasites 

 partially enclosed in red cell ; 6, 7, parasites in human blood ; <?-//, parasites in lungs of the 

 monkey, Callilhrix ; 12, jj, initial forms of schizogony ; 14, 75, schizogony in the lungs of 

 Callithrix. (After Chagas.) 



The dimorphism has been interpreted sexually, the first mentioned 

 forms being termed males, the second ones females. The correctness 

 of this interpretation is very doubtful. 



No sign of longitudinal division was ever seen in the peripheral 

 blood or in the internal organs. The " endocorpuscular " forms may 

 be completely or partially enclosed in the red cell or only attached 

 thereto (fig. 33, 1-5). At the beginning of infection the endocor- 

 puscular forms are the more numerous. Some authorities, however, 

 doubt these stages. 



Life-history in the Vertebrate Host. Chagas found fluctuations in 

 the number of the parasites in the peripheral blood. He believes the 

 increase of the parasites to be periodic. 



