772 



PATHOGENIC PROTOZOA 



parasites are almost never seen in the peripheral blood in aestivo- 

 autumnal fever, though in tertian they are common and in quartan 

 numerous. If, however, films are prepared at autopsy from the 

 spleen, liver, bone marrow and brain, enormous numbers of segment- 

 ing forms, together with all other stages of the parasite, may be found. 

 The full grown segmenter occupies one-third to one-half the cell and 

 shows a collection of hemozoin in large blocks in the center. The 

 merozoites vary in number from eight to twenty -five. In addition 

 to the small and large rings the peripheral blood shows, after the fever 

 has lasted sufficiently long, the sexual forms or gametes. The infected 

 erythrocyte is never stippled nor swollen, but, on the contrary, may 

 appear shrunken. Both the micro- and macrogametocytes in aastivo- 

 autumnal fever are crescentic in shape, their length being about one 



and one-half and the width about 

 one-half that of an erythrocyte; 

 the pigment is collected toward the 

 center, which is rather paler in 

 stained specimens than the poles. 



f&%* At first sight the gametes appear 



to lie free in the plasma, yet in 

 vWL* *NJr stained specimens a rim or rib of 



the pale red cell may be seen on 

 ^ K^^ the concave side. When liberated 



from the erythrocyte the gamete 

 becomes first spindle-shaped and 

 finally oval or round. The male 

 crescent is short and broad, and 

 the female relatively long and 

 slender. 



The Finer Structure of the Plasmodia. The finer details, wnich 

 are only hinted at in fresh specimens and in those stained with Man- 

 son's stain, can be studied to advantage in those stained with some 

 one of the many modifications of the Romanowski stain, such as that 

 of Wright, Hastings, MacNeal or Giemsa. 



The tertian parasite, which lies in a red cell, may be seen to be 

 divided into a blue cytoplasm and a brilliant red nucleus, and it 

 would be well for the novice to remember that these three conditions 

 must be satisfied before the diagnosis of malaria can be made; the 

 principal stumbling-block is the blood platelet, often found overlying 

 a red cell, but it, although possessing a ragged blue cytoplasm, has al- 





FIQ. 193. PLASMODIUM FALCIPARUM. 

 (X 1500.) (Army Med. School Col- 

 lection, Washington, D. C.) 



