110 TRYPANOSOMES AND SLEEPING SICKNESS 



different parasite. The real method of multiplication was first 

 discovered by Vianna in the bodies of man and animals who had 

 died of the disease. Vianna found in various tissues, especially in 

 the walls of the heart, the striped muscles, the central nervous 

 system and various glands, greatly swollen cells which served as 

 cysts, enclosing a mass of rapidly dividing trypanosomes, varying 

 in number from just a few to many hundreds. In younger cysts 

 the parasites are round in form and exactly resemble Leishman 

 bodies (Fig. 26 A), while in older cysts the flagellum can be seen 

 on many individuals and the trypanosome form becomes evident 

 (Fig. 26B). When the enclosing cell has swollen to the bursting 

 point, the swarming mass of trypanosomes is liberated. Each 

 parasite, unless destroyed, then penetrates a new cell somewhere 

 in the body, usually near where it originated, and begins the 

 process of reproduction again. Only in the early acute stage of 

 the disease can the parasites live in the blood, since the blood 

 serum rapidly reacts by the formation of antibodies, and be- 

 comes deadly to trypanosomes. Chagas believed that the para- 

 sites could live within the corpuscles as well as in the serum, but 



later work does not confirm this. 

 On account of the development of 

 antibodies in the blood serum, the 

 parasites are very seldom found in 

 the blood of chronic cases of the 

 disease, though their cysts may be 

 abundant in various tissues and 

 glands in the body. 

 FIG. 27. Trypanosoma cruzi in Life Cycle in Bugs, and Trans- 

 biood of ape said to be inside cor- mission. The intermediate host 



puscles. (After Chagas.) . . 



of Trypanosoma cruzi is a large 



black and red bug, Triatoma megista, known to the natives as 

 "barbeiro." It is related to the cone-nose, Triatoma sanguisuga, 

 of our southern states. The barbeiro is a fierce blood-sucking 

 insect which infests the dirty thatched or mud houses of the 

 natives, coming out at night and skillfully secreting itself in the 

 daytime (see p. 379, and Fig. 168). 



It was found that the bugs in the houses where Chagas' disease 

 had been observed were invariably infected with trypanosomes 

 in their gut, and from this fact and from the habits of the bug 

 Chagas rightly deduced and later proved that the bug was the 



