33 MANUAL OF BACTERIOLOGY. 



The Malarial Parasite. 1 (Plasmodium or Hematozoon 

 Malaria). The organisms of malaria consist of at least 

 three different species, each associated with one of the three 

 types of malarial fever: The tertian parasite with benign 

 tertian malarial fever, the parasite reaching maturity in 

 forty-eight hours; the quartan parasite with benign quar- 

 tan malarial fever, the cycle of development requiring 

 seventy-two hours; and the &stivo-autumnal parasite with 

 malignant, aestivo-autumnal fever, developing to maturity 

 in a variable period of from twenty-four to forty-eight 

 hours. The parasites are studied to best advantage in a 

 drop of fresh, fluid blood placed between a cover-glass and 

 slide and examined with an oil-immersion objective. For 

 method of making and staining dry preparations, see pages 

 55 and 108. 



Tertian Parasite. This appears in its youngest form as 

 a small, round, colorless, hyaline body within the red cor- 

 puscle, seen during and just after the chill of the disease. 

 This body may be actively amu'boid. suddenly changing its 

 contour into various forms. Its size gradually increases, 

 and fine, dark, actively-motile, dancing pigment granules 

 begin to appear at its periphery. 



The red corpuscle harboring the parasite, with the growth 

 of the latter, becomes gradually paler and expands in size. 

 The parasite as it grows loses its earlier amoeboid movement 

 and the pigment granules, still actively motile, accumulate. 

 Xear the end of forty-eight hours, the organism finally fills 

 the red corpuscle, only a faint rim indicating the latter. The 

 ripe parasite now divides it into from fifteen to twenty-live 

 small, round, hyaline spores which are arranged somewhat 

 radially about the pigment granules which have lost their 

 motility and become concentrated in a clump at the center of 



1 Thaver and llewetson, "The Malarial Fevers of Kaltimore." Johns 

 Hopkins Hospital Reports, iS<>5. Vol. V., and reprinted; Thayer, "Lec- 

 tures on the Alalarial Fevers," Xe\v York, 



