APPENDIX. 331 



The Malarial Parasite* (Plasmodium or Hgematozoon 

 malarise). — 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 quartan malarial 

 fever, the cycle of development requiring seventy- two hours; 

 and the estivo-autumnal parasite with malignant, estivo-autum- 

 nal 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 44 and 97. 



Tertian Parasite. — This appears in its youngest form as a 

 small, round, colorless, hyaline body within the red corpuscle, 

 seen during and just after the chill of the disease. This body 

 may be actively ameboid, 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 earher ameboid movement, 

 and the pigment granules, still actively motile, accumulate. 

 Near 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-five 

 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 



* Thayer and Hewetson. The Malarial Fevers of Baltimore. Johns Hop- 

 kins Hospital Reports. Vol. V. 1895. Thayer. Lectures on the Malarial 

 Fevers. New York. 1897. 



