428 TRYPANOSOMIDM 



The free forms are also differentiated into two forms — viz., one 

 with a large egg-shaped kinetonucleus, with a chromatic appendage, 

 and with an oval or band-like trophonucleus with a centrosome. 

 The flagellum starts from the kinetonucleus or from its chromatic 

 appendage. 



In the second free form the kinetonucleus is round and smaller 

 than the first, and has, as a rule, no chromatic appendage. This 

 form is broader than the one previously described. Whether this 

 is a sexual differentiation or not is unknown. 



The intraglobular forms may be completely or partially enclosed 

 in the red cell, or merely attached by the afiagellar end. 



Measurements of these forms were not originally given by Chagas, 

 but it would appear as though the average length was 20 /j., with a 

 certain amount of variation. 



Life-History — Schizogony, — 5. cruzi is remarkable in that it is 

 not known to undergo longitudinal division either in the peripheral 



blood or the internal organs of its host. 

 According to Chagas, there is a regular 

 cyclic development, the parasite entering 

 the capillaries of the lungs, where it loses 

 its flagellum and undulating membrane, 

 while the trophonucleus moves nearer 

 the flagellar end, and the whole parasite 

 becomes curved, first into a half-moon, 

 and finally so much that the two ends 

 fuse, forming a ring and finally a disc. 

 In some instances the kinetonucleus dis- 

 appears, while in others it fuses with the 

 trophonucleus, after which the nucleus 

 divides into eight, and eventually gives 

 rise to eight merozoites lying inside the 

 periplast, which acts like a cyst wall. 

 The merozoites with kinetonuclei are con- 

 sidered to be microgametes, and those without kinetonuclei to be 

 macrogametes. The merozoites escape from the periplast wall 

 singly, and, entering the red blood cells, become flagellates, and, 

 finally leaving the red cell, become free in the liquor sanguinis, 

 thus completing the cycle of gametogony, or differentiation and 

 multiplication of gametes. 



Agamogony, or asexual reproduction, takes place in the cells of 

 various organs — i.e., in hypertrophied endothelial cells in the lungs, 

 in the cardiac muscle, in the neuroglia of the central nervous system, 

 and in striped muscle. In these situations the parasite appears 

 as a rounded body with trophonucleus and kinetonucleus, but with- 

 out flagellum or undulating membrane. Agamogony increases the 

 number of parasites in the host, and is responsible for the production 

 of the symptoms, while gametogony differentiates the sexual forms, 

 and presumably lays the basis for the infection of the invertebrate 

 host. This form of development is confirmed by Brumpt, 



Fig. 114. — Transverse 

 Section of a Striated 

 Muscle, containing S. 

 cvuzi Chagas in the 

 Centr AL Portion. 

 (X 1,363.) 



(After Vianna.) 



