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The parasite.—Laverania malariæ (Plasmodium falciparum, Blan.)—the usual parasite (Fig. 21) of malignant infection—is, in many respects, like that of ordinary tertian, only smaller, attaining when mature from a half to two-thirds the size of the corpuscle it occupies. The infected blood-corpuscle may be altered in colour in the direction of being either darker or lighter; sometimes it shrinks, or it may become a "brassy body." The segments of the rarely encountered mature segmenting parasite number usually ten or twelve, and are arranged along with the associated clump or clumps of hæmo Fig. 21.—Evolution of the subtertian parasite: asexual cycle.

zoin in an irregular heap. The crescent-shaped gametocyte is a characteristic feature.

The fever.—The associated symptoms are, in many respects, very different from those caused by the tertian parasite. In the first place, although rigor is not so marked, the hot stage lasts longer—often exceeding twenty-four hours; in fact, the tendency for the successive paroxysms to overlap, to become subintrant, is very marked. Moreover, where the intermissions are distinct, as Marchiafava and Bignami point out, the crisis is generally unlike that of ordinary tertian. There is frequently what is called a "double crisis"; that is to say, when the fever has attained its apparent fastigium there is a drop of one or more degrees of temperature—the "false crisis"—to be followed by a fresh rise, which is then followed