768 



PATHOGENIC P&OTOZOA 



occupied by the parasite is stippled, that is, dotted with reddish gran- 

 ules called Schu-ffner's dots, and, as the swollen red cell and Schuff- 

 ner's dots are found in no other form of malaria, their presence is 

 pathognomonie of tertian. 



The youngest form, the free merozoite, is rarely seen, but young 

 comet-like forms composed of a particle of red chromatin and a little 

 blue cytoplasm may readily be detected at the height of the fever; 

 that is, a few hours after the chill and sporulation. The round, young 

 schizont as it grows develops early a central vacuole and assumes 

 the shape of a signet ring, the red chromatin dot being the stone. This 



FIG. 187. PLASMODIUM VIVAX. (Army Med. School Collection, Washington, D. C.) 



small tertian ring grows rapidly as the fever subsides, and at the 

 same time the infected cell increases in size. Twenty-four hours after 

 the chill the ring has grown so much that it is referred to as the large 

 tertian ring, and its tendency to irregularities of shape and ameboid 

 form becomes apparent, and fine granules of pigment, called melanin 

 or hemozoin, begin to be visible. After thirty -six hours the rings will 

 all have grown into large ameboid forms. After about forty hours the 

 parasite occupies almost the entire cell and the pigment begins to col- 

 lect in masses toward the center. Soon after the first signs of seg- 

 mentation appear, which becomes more and more distinct until fifteen 

 'to twenty separate segments or merozoites are seen, each composed 



