THE PATHOGENIC HEMOSPORID1A 285 



ever, see p. 287). After some twenty-four hours the plasm of- the 

 ring form collects at one point, giving the effect of a signet ring, and the 

 pigment granules first appear in the thickened portion. After about 

 thirty hours the majority of the parasites have disappeared from the 

 peripheral circulation, although a few may be found, especially in the 

 Italian forms of the disease. In such cases the parasites, after thirty- 

 six hours, appear round or oval and very sharply contoured, occupying 

 from one-fifth to one-fourth of the whole volume of the corpuscle, which 

 now begins to shrink. The chromatin divides (Plate II, 17 to 20, a) 

 and the body of the parasite breaks up into from 12 to 16 merozoites, 

 although the number of these may vary anywhere from 8 to 24 

 (Ziemann). 



By analogy with other parasitic protozoa this process of asexual 

 multiplication may continue for a longer or shorter time, or until the 

 vitality is exhausted. A period finally ensues, the conditions being 

 unknown, in which the merozoites develop into the sexual phases of the 

 organism. These are the macrogametocytes and microgametocytes, 

 the former female organisms, the latter mother cells of the male 

 organisms. The stages in this development in the case of Plasmodiu m 

 vivax are shown in Plate III, Fig. 1. The female organism is a large 

 cell with reserve granules and a well-developed nucleus. The male 

 mother cell is less granular and its nucleus divides by a multiple divi- 

 sion into a number of daughter nuclei which migrate to the periphery 

 and there become the long-drawn-out nuclei of the flagelliform micro- 

 gametes. The female nucleus, before fertilization, divides to form a 

 small nucleus, which is extruded from the cell, this corresponding to 

 the polar body equivalent of other protozoa and metazoa (Schaudinn). 



The processes thus briefly outlined do not all occur in the human 

 blood. The early stages of gametocyte formation occur there while 

 the remaining stages, viz., gamete formation and maturation processes, 

 occur in the gut of a mosquito. Schaudinn had reason to believe that 

 these sexual reproductive stages, especially of the microgametocytes, 

 degenerate in the blood and come to nothing unless stimulated to 

 development by the action of a cooler medium, such as room tempera- 

 ture or the cool medium of an insect's body. The organisms ready for 

 this further development are constantly in the blood after the first few 

 paroxysms, and when sucked up by the mosquito, the further changes 

 take place rapidly in the latter's stomach and fertilization is brought 

 about by the penetration of one of the slender microgametes into a 

 macrogamete. The fertilized cell, called by Schaudinn the ookinet, 

 now makes its way by a peculiar vermiform movement (giving rise to 

 the name vermicule) to the epithelial cells lining the gut; it penetrates 

 the mucous membrane and comes to rest in the submucosa. Here it 

 rapidly grows into an organism of the size of a coccidium, the nucleus 

 divides, and the cell body, at about the third or fourth day, forms 



