PLASMODIUM VIVAX 225 



nine or twelve pear-shaped bodies, or merozoites. These separate 

 from each other and individually attack a fresh red cell, and this 

 attack brings about another paroxysm of fever seventy-two hours 

 after the previous one. The grains of pigment are taken up by the 

 leucocytes, and deposited in the spleen and bone marrow. 



The nucleus of the parasite may be seen if suitably stained. The 

 double or triple quartan is explained by the fact that there are two 

 or three groups of organisms that undergo sporogony at periods 

 separated from each by twenty-four hours. 



PLASMODIUM VIVAX (Grassi). 



The cause of tertian fever occurring in the spring. It differs 

 from the Plasmodium malaria because of shorter period (forty- 

 eight hours) consumed in schizogony (or sporulation) , the much 

 greater activity of the amoeboid movement, and the affected corpus- 

 cles becoming enlarged; also by the fact that many of the melanin- 

 bearing stages are visible. The schizogony is rarely apparent 

 in the circulating blood, but in the spleen these stages are easily 

 seen. There are from fifteen to twenty merozoites (segmented 

 bodies or spores) which are arranged in an irregular heap, but not 

 radially like wheel spokes. The merozoites are smaller than the 

 quartan variety and are more numerous. The flagellated form can 

 but rarely be seen in the freshly drawn blood. If some blood, con- 

 taining the large extra-corpuscular bodies, is put in a moist chamber, 

 they throw out flagella. These flagella are really micro 'gametes and 

 are sexually active. The extra-corpuscular bodies are partly mac- 

 rogametes, and if they become flagellated they are called polymites, 

 and are the micro gametocytes. The merozoites or spores, finally 

 burst forth from the erythrocytes, starting again another cycle 

 (attended with a paroxysm of fever). These spores appear in the 

 freshly invaded corpuscles as hyaline bodies with slight movement. 

 As they grow in size, pigment appears in the protoplasm. Certain 

 of these do not break up into merozoites, or spores, but become extra- 

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