THE PATHOGENIC HEMOSPORIDIA 283 



3. Estivo-autumnal Parasite (Plasmodium falciparum) (Plate II). 



Young forms alone found in peripheral circulation; very small, 

 occupying from one-fourth to one-half the corpuscle. 



Melanin scarce, a few (2 to 3) granules usually central in position. 



Merozoites, 6 to 15, formed at twenty-four to forty-eight hour 

 intervals (see Figs. Ill and 112). 



Ameboid activity marked, but less than that of vivax. 



Macrogamete at first crescentic in form. 



Effects slight shrinkage and often crenulation of corpuscles. 



Incubation period usually from ten to twelve days. 

 As an example of the asexual reproduction of the malaria organisms 

 we may select the cause of tertian fever, Plasmodium vivax, which has 

 been carefully worked out and described by Schaudinn. The young 

 sporozoite from the mosquito was studied in the living state and every 

 stage confirmed in preparations. With characteristic ingenuity he 

 succeeded in getting his own blood in sufficiently dilute condition to 

 follow the movements of the young sporozoite in life. This he did by 

 raising a blister on his hand and then teasing the contents of an infected 

 mosquito's salivary gland into the fluid obtained from the blister; the 

 blood corpuscles were thus relatively few in number, and with a warm 

 stage he was able to follow the history of the parasites for hours. The 

 young forms grow into a large organism which may nearly fill the 

 erythrocyte. In the course of its growth a vacuole appears in the 

 vicinity of the nucleus, probably due, as Schaudinn believed, to the 

 active processes going on in the vicinity of the parasite's nucleus. 

 In this way the ring-forms of the parasite are formed, the vacuole 

 increasing relatively in size. Ewing ('98) interpreted these ring- 

 forms as due to the coalescence of two horn-like pseudopodia, the 

 vacuole thus arising in a purely fortuitous manner, and Argutinsky 

 interpreted them as artefacts. Schaudinn's observations on the living- 

 organisms and his seeing this vacuole appear and disappear indicate 

 that the vacuole and the ring forms are only evidences of physiological 

 stages of the parasite, the vacuole serving only to increase the surface 

 of absorption in relation to volume. It is not without significance, 

 either, that he did not observe the formation of the vaucole in the 

 sexual cycle. The nucleus of the young form consists of a relatively 

 large karyosome and a minute vesicular part, the karyosome finally 

 becoming granular and then dividing, the division being of a very primi- 

 tive type of mitosis. At this period, which marks the full growth of the 

 schizont, the organism becomes extremely motile within the blood cor- 

 puscle (Plate I, Fig. 1). Schaudinn graphically describes it as follows: 

 'This period of the highest development of its vegetative activity is 

 characterized by an important increase of its ameboid motion. It 

 assumes the most unusual forms and is not for a moment at rest. The 

 pigment becomes distributed throughout the body, long pseudopodia are 



