54 WALKER. 



factor, for reasons that will be apparent later, is named Schizo- 

 trypanum cruzi. This trypanosome is said not to multiply by 

 simple division in the peripheral blood, but instead to undergo 

 schizogony in the capillaries of the lungs of the infected animal. 

 This reproductive process takes place at the time of the increase 

 of the trypanosomes in the blood, especially at five to six days 

 after inoculation of the animal and, also, during the great in- 

 crease of the parasites which occurs just previous to the death 

 of the infected animal. The trypanosome sheds its flagellum 

 and undulating membrane, bends upon itself, and becomes fused 

 into a round or oval body. In some of these bodies, the blepharo- 

 plast is shed with the flagellum, in others it is retained. By 

 division of the nucleus in the first form and of the nucleus and 

 blepharoplast in the second form, and by a differentiation of the 

 protoplasm there are developed from these bodies schizocysts 

 containing 8 small club-shaped merozoites. The merozoites 

 escape from the cyst and penetrate red blood-corpuscles, where 

 they develop into trypanosomes. When fully developed, they 

 leave the blood-corpuscles and live free in the plasma. The 

 blepharoplast-less merozoites develop into female trypanosomes, 

 having a small blepharoplast derived from the nucleus through 

 heteropolar division, a round nucleus, and a broad body; the 

 merozoites having a blepharoplast develop into male trypano- 

 somes having a large blepharoplast, an elongated nucleus, and 

 a slender body. 



Hartmann, in 1910, found in a section of the lung of a guinea 

 pig infected with Schizotrypaniim cruzi Chagas, greatly hyper- 

 trophied endothelial cells containing large numbers of more or 

 less pyriform, binucleate bodies. Similar intracellular stages, 

 Hartmann states, were subsequently found by Chagas in the heart 

 musculature and in the brain of a man dead from schizotrypa- 

 nosomiasis. He believes that this intracellular multiplication 

 represents the true schizogony, while the extracellular schizo- 

 gony with a sexual differentiation of the products of division, 

 previously described by Chagas, is considered a gametogony. 

 Carini (1911) has described a similar so-called schizogony of 

 Trypanosoma leptodactyli in endothelial cells in the blood from 

 the heart of an infected animal (Leptodactylus ocellatus). 



Fantham (1911) has recently studied the life history of Try- 

 panosoma gambiense and Trypanosoma rhodesiense in relation 

 to the number of trypanosomes in the peripheral circulation, 

 making use of the thick film method of Ross to determine ac- 

 curately the number of trypanosomes in the blood from day to 



