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58 met with, the associated fever is probably remittent, irregular, or more or less continued in type.

The foregoing are generalities which apply to all the types of malarial infection.

The parasite.—The parasite of quartan fever, Plasmodium malariæ (Fig. 20), has a cycle of seventy-two hours. At its earliest stages of epicorpuscular and of early unpigmented intracorpuscular life it takes the form of a small, roundish, clear speck (Plate I., Fig. 1, a), showing up somewhat distinctly against the hæmoglobin of the invaded corpuscle. At this stage, as contrasted with the other species of malaria parasites, it is further

Fig. 20.—Quartan parasite: asexual stage: stained.

distinguished by the feebleness of its amœboid movement. Later, as soon as it becomes pigmented (Fig. 20, b, c, d, e, f), all amœboid movement ceases. (See also Plate I., Fig. 1, b, c, d, e, f.) Relatively to the other malaria parasites, the hæmozoin carried by the quartan is large in amount and coarse in grain, sometimes forming short rods. The segmented or mature parasite (Fig. 20, g, h) is made up of eight to ten elements arranged daisy-fashion and, generally, very symmetrically around the now centrally placed and massive block of very black hæmozoin. About the centre in each of the spherical or pear-shaped segments, which are slightly rough in outline, a shining nucleolus can usually be readily made out.

The gametocyte, or sexual form, is a spherical