APPENDIX. 333 



extra-cellular forms are smaller than those of the tertian, 

 being about the size of a red corpuscle, and contain coarse 

 pigment granules in active motility until degeneration 

 occurs. Flagella may develop from certain extra-cellular 

 forms. The entire development of the quartan parasite 

 occupies about seventy-two hours. 



/Estwo-autumnal Parasite. This parasite develops to 

 maturity in from twenty-four to forty-eight hours and is 

 usually regarded as representing a single species, though 

 certain observers claim to distinguish two distinct varieties. 

 The usual description of a single variety is here adopted. 

 The youngest forms (hyaline bodies) resemble those of the 

 tertian and quartan organisms, but are distinctly smaller and 

 more highly refractive. They often present a ring-like 

 appearance. They are amoeboid. Pigment granules later 

 appear at their periphery, 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 diffi- 

 culty 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 circulating blood in early 

 infections; the mature forms, with the exception of the 

 extra-cellular 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 arrange- 

 ment, but are much smaller in the aggregate, as well as in 

 the individual segments. 



After the fever has lasted about one week, extra-cellular 

 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 



