SPOROZOA 



1111 



the normal erythrocyte until after the latter has raptured, but when 

 free in the plasma it is practically impossible' 1o distinguish them 

 from tertians. 



Plasmodium falciparum. The parasite of a^stivo-autumnal fever, 

 I'lfisnifHlinm falciparum, differs considerably from the two forms al- 

 ready described; the life cycle varies between twenty-four and forty- 

 eight hours, and, at least in new infections, only ring forms are 

 found in the peripheral blood, although at a later stage crescentic 

 gametocytes may be present. The youngest aestlvo-autumnal rings, 

 found at the height of the fever, are more delicate than the younp; 

 tertians. As the temperature falls the rings increase in size, but 



FIG. 157. PLASMODIUM MALARLE. 

 (Army Med. School Collection, Wash- 

 ington, D. C.) 



FIG. 158. PLASMODIUM FALCIPARUM. 

 (X 150.0) (Army Med. School Col- 

 lection, Washington, D. C.) 



without change of form; the growth is not uniform, but occurs as 

 a thick crescentic swelling on the convex surface of the ring, and 

 occasionally more than one such swelling is present. The large 

 aestivo-autumnal ring, found after the febrile paroxysm has passed, 

 occupies one-third to one-half the red cell, which is never swollen 

 nor stippled, as in tertian, and the parasite is never band-like, as 

 in quartan. Segmenting 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 segmenting forms, together with all other stages of the 

 parasite, may be found. The full grown segment cr occupies one- 

 third to one-half the cell and shows a collection of hemozoin in large 



