608 Malaria 



completed in the visceral capillaries. Hence, the young rings, formed 

 shortly after merozoites invade fresh corpuscles, are normally the youngest 

 stages seen in blood smears. A characteristic feature is the fairly common 

 appearance of several, sometimes as many as six, small rings in one 

 corpuscle. The young ring usually measures not more than one-sixth the 

 diameter of the corpuscle. A thin film of cytoplasm encloses the vacuole 

 and the nuclear material is often seen as a small granule apparently 

 projecting from the outer surface of the ring. Occasionally, the chromatin 

 mass is rod-shaped, or there may be two or more small granules instead 

 of one. Early growth stages develop a thicker cytoplasmic layer, become 

 somewhat irregular in outline, and deposit dark brow-n or black pigment 

 granules. These larger and somewhat irregular rings, less amoeboid than 

 in P. v'wax, are probably comparable to half-grown forms of the latter. 



The invaded corpuscle does not become enlarged, does not show 

 Schiiffner's dots, and may stain a little more intensely than the normal 

 corpuscle. Relatively coarse irregular eosinophilic granules i^Mmirer's 

 dots) are seen rather rarely, but small basophilic granules (dots of 

 Stephens and Christopher) may be expected somewhat more frequently. 



In severe cases, particularly those with an unfavorable prognosis, all 

 stages of development may be found in blood smears. Ordinarily, how- 

 ever, grow'th stages remain in the peripheral circulation for about 24 

 hours and then drop out in the capillaries of the spleen, bone marrow, 

 and other internal organs where merogony is completed. Late stages 

 of growth and merogony have been observed also in dermal tissue smears 

 from children (79). This characteristic lagging of the older stages in 

 visceral capillaries is possibly the result of an acquired adhesiveness of 

 the invaded corpuscles, which tend to stick together and to the capillary 

 endothelium. 



In the later stages the vacuole disappears and the cytoplasm appears 

 denser. This compact stage, shortly before nuclear division begins, is 

 not much larger than the largest rings seen in the peripheral blood. The 

 mature schizont, in which the pigment may occupy almost a third of the 

 cytoplasm, usually measures not more than two-thirds the diameter of 

 the corpuscle. Merogony produces 8-24 merozoites which measure 1.0[x or 

 less. 



The early development of gametocytes occurs typically in the visceral 

 capillaries. As it reaches the peripheral circulation, the mature gameto- 

 cyte varies in form, even within a single strain (58, 59). Most commonly, 

 both types of gametocytes are sausage-shaped rather than crescentic. As 

 a rule, the two show fairly distinct differences, but there may be some 

 intergradation between gametocytes which are not quite mature. The 

 mature microgametocyte usually shows a fairly large, lightly stained 

 nucleus. The smaller nucleus of the macrogametocyte stains a little more 

 deeply. The cytoplasm of the macrogametocyte stains a rather deep blue; 



