334 MANUAL OF BACTERIOLOGY. 



tian segmenting parasite. The quartan extracellular forms 

 are smaller than those of the tertian, being about the size of a 

 red corpuscle, and contain coarse pigment granules in active 

 motihty until degeneration occurs. Flagella may develop from 

 certain extracellular forms. The entire development of the 

 quartan parasite occupies about seventy-two hours. 



Estivo-autumnal Parasite. — ^This parasite develops to ma- 

 turity in from twenty-four to forty-eight hours, and is usually 

 regarded as representing a single species, though certain ob- 

 servers claim to distinguish two distinct varieties. The usual 

 description of a single variety is here adopted. The youngest 

 forms (hyahne bodies) resemble those of the tertian and quar- 

 tan organisms, but are distinctly smaller and more highly 

 refractive. They often present a ring-like appearance. They 

 are ameboid. Pigment granules later appear at their per- 

 iphery, but are exceedingly minute and scanty, seldom more 

 than one or two being seen. These granules have little or no 

 motihty, and in fact are with difficulty made out. The hyaline 

 bodies remain small, seldom exceeding one-third the diameter 

 of a red corpuscle. The infected corpuscle is apt to be crenated, 

 shrunken and dark. These are the forms seen in the circu- 

 lating blood in early infections; the mature forms, with the 

 exception of the extracellular forms, developing in the spleen 

 and bone-marrow, rarely reach the general circulation. Blood 

 from the spleen shows the full-grown forms in abundance. The 

 segmenting forms resemble those of the tertian parasite both 

 in the numbers of the segments and in their arrangement, 

 but are much smaller in the aggregate, as well as in the indi- 

 vidual segments. 



After the fever has lasted about one week, extracellular 

 forms make their appearance in the circulating blood. These 

 are crescentic, ovoid or small round bodies, containing coarse 

 pigment granules at their center, generally arranged in a 

 ring. The crescents and ovoid bodies are highly refractive 



