SPOROZOA 



1107 



easily in fresh specimens, the following description applies to those 

 stained with some form of the Romanowski stain. 



Plasmodium vivax. The parasite of tertian fever has a life cycle 

 lasting forty-eight hours arid is easily recognized only when full 

 grown, that is, twenty-four to forty-eight hours after the chill. 

 While a diagnosis may be made on younger forms, it is not so readily 

 made. As its name implies, the Plasmodium vivax is actively ame- 

 boid, and pseudopods and irregular outlines characterize the well- 

 grown parasite; the infected erythrocyte is swollen, often to twice 



FIG. 151. PLASMODIUM VIVAX, AN ATYPICAL 

 MACROGAMETOCYTE. Form interpreted 

 by Schaudinn as undergoing partheno- 

 genesis. (Army Med. School Collection, 

 Washington, D. C.) 



FIG. 152. PLASMOD'IUM VIVAX 

 (Army. Med. School Collection, 

 Washington, D. C.) 



its normal size, the hemoglobin is pale and, especially in spreads 

 in which Hanson's stain has been used, it is so much paler than 

 in the surrounding cells that the infected cell stands out clearly. 

 The part of the cell unoccupied by the parasite is stippled, that is, 

 dotted with reddish granules called Schuffner's dots, and, as the 

 swollen red cell and Schuffner's dots are found in no other form 

 of malaria, their presence is pathognomoriic 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 



