282 THE PATHOGENIC HEMOSPORIDIA 



(schizogony) of the parasites in the blood. Coming from the same 

 original brood, the parasites in the blood all sporulate at the same 

 time; this results in a constantly increasing number of reproductive 

 bodies being liberated at stated intervals. At first the young forms 

 are too few to cause any serious trouble, and there is no reaction on the 

 part of the host. This is the period of incubation (ten to twelve days) 

 of the disease, but with the increase in numbers of merozoites there is 

 a continuous army of invaders, increasing in geometrical progression 

 and entering the blood corpuscles until finally the numbers are incredi- 

 bly large. With each invasion occurring every day or every three days 

 or every four days, according to the nature of the parasite, there is a 

 marked anemia and poisoning, which tend to produce cachexia and 

 sometimes death. Fever coincides with the liberation of new swarms 

 of merozoites, as shown in the accompanying charts or fever curves 

 (Figs. 109 to 112). At the time of merozoite formation waste matters that 

 have accrued as products of the parasite's metabolism and kept stored 

 up in the body of the parasite are liberated and help in the general 

 intoxication of the victim. These are modified products of hemoglobin 

 digestion on the part of the parasite, and, known as the melanin 

 granules, they are collected from the blood and stored in the liver, 

 kidney, or spleen, or even in the lungs and brain, leading to pigmenta- 

 tion of these organs and frequently to hypertrophy, more especially of 

 the spleen and liver. 



The essential differences between the parasites of tertian, quartan, 

 and estivo-autumnal fevers may be briefly summarized as follows : 



1. Tertian Parasite (Plasmodium vivax) (Plate I, Fig. 1). 



Young schizonts from 1 to 3 /x up to the size of normal blood 



corpuscles. 

 Melanin granules distributed throughout protoplasm or (at 



schizogony) collected at one point on periphery. 

 Merozoites, 12 to 24, formed every forty-eight hours. Peripheral 



circulation (see also Fig. 109). 

 Ameboid activity very pronounced, 

 Macrogametes spherical. 

 Effects slight enlargement of corpuscle. 

 Incubation period about fourteen days. 



2. Quartan Parasite (Plasmodium malariae) (Plate I, Fig. 2). 



Size as above, but never as large as normal corpuscle. 



Melanin granules not distributed; collected in zone on periphery. 



Merozoites, 6 to 12, formed every seventy-two hours. Frequent 



in circulation (see Fig. 110). 

 Relatively quiescent in the corpuscle. 

 Macrogametes spherical; less numerous than in vivax. 

 Effects no enlargement, frequently shrinkage of corpuscle. 

 Incubation period about three weeks. 



