PATHOGENIC PROTOZOA. 421 



forms (hyaline 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 

 motility, 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 

 and are in length about equal to the diameter of a red cor- 

 puscle, sometimes larger. The round forms are smaller than 

 a red corpuscle, with the pigment arranged centrally in a 

 ring. They may become flagellated after the blood has 

 remained outside the body for some minutes. Any of the 

 extracellular bodies may show remnants of the red corpuscle 

 attached to its side, like a bib. The extracellular forms are 

 concerned in the cycle of development of the organism in the 

 mosquito, and are sterile in the human body. They are 

 exceedingly resistant to quinine and may continue in the blood 

 for long periods of time. 



