TRYPANOSOMA CRUZI 85 



The investigations of Chagas and of Hartmann have revealed two 

 types of multiplication which take place in the internal organs of the 

 vertebrate host. 



(a) The first type which possibly belongs to another organism, 

 Pneumocystis carinii, see p. 90 occurs in the capillaries of the lungs. 

 The flagellate parasite entering the lung capillaries loses its flagellum 

 and undulating membrane. Its body becomes curved, and the two 

 ends fuse, and so an oval mass is formed (fig. 33, #-//). In some 

 cases the blepharoplast disappears, in other cases it blends or fuses 

 with the nucleus. The nucleus of the rounded parasite then divides 

 into eight by successive divisions (fig. 33, 1.2-15). Next the body, 

 which is surrounded by its own periplast, also divides, giving rise 

 to eight tiny daughter individuals or merozoites (fig. 33, 75). The 

 merozoites lie inside the periplast, which acts as a sort of " cyst 

 wall." The merozoites are said to exhibit dimorphism, and Chagas 

 has interpreted the dimorphism in terms of sex. The daughter forms, 

 produced by the parent trypanosomes which kept their blepharoplasts, 

 themselves have blepharoplasts as well as nuclei, and have been termed 

 "males" or " microgametes." The merozoites, arising from parent 

 trypanosomes which lost their blepharoplasts, have themselves only 

 nuclei, and have been called "females" or " macrogametes." In the 

 case of the so-called "female" forms the single nucleus divides into 

 two unequal parts, of which the smaller becomes the blepharoplast, 

 and a flagellum is formed later. The so-called " males " possess early 

 a rudiment of a flagellum. Both kinds of merozoites escape from the 

 parent periplast wall, and enter red blood corpuscles. They grow into 

 flagellates within the corpuscles, and then become 



free as adult trypanosomes in the blood-stream. 



(b) The second mode of multiplication 

 is one of asexual reproduction (schizogony 

 or agamogony). It was first described by 

 Hartmann from hypertfophied endothelial cells 

 of the lungs. It has since been found in the 

 cardiac muscle, in the neuroglia of the central 



nervous system, and in striped muscle (fig. 34). FIG. 34. Trypanosoma 



In laboratory animals it has also been found <- Transverse section 



,. . . - , , of a striated muscle con- 



Ill the testicle and suprarenal capsules. In taining rounded forms of 

 these tissues the parasite is intracellular, ap- the .parasite in the central 



,, . portion. X ijOOO approx. 



peanng as a small rounded body with nucleus (After vianna.) 



and blepharoplast, without flagellum or undu- 



lating membrane. In other words the parasite is Leislnnania-like in 



the body tissues, and recalls the organism of kala-azar. 



Chagas considers this second mode of multiplication to be strictly 

 asexual. By this means the number of parasites in the vertebrate 



