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III] impressed on it originally by the shape of the corpuscle, to something more approaching a globular form.

In the tertian, as in the quartan parasite, the gametocyte is a spherical body resembling closely the mature parasite from which the segmented body is evolved (Plate I., Fig. 2, j). It is seen more particularly, just as in the case of the quartan infection, after and not infrequently about the time of rigor. The tertian gametocyte is considerably larger than that of the quartan and subtertian parasite.

Chart 2.—Benign tertian ague.

Geographical distribution.—The tertian parasite, probably the commonest form of malaria parasite, occurs in temperate and tropical latitudes alike. It is often met with as a double infection, and is, perhaps, the most frequent cause of quotidian as well as of tertian agues.

The fever.—The fever it gives rise to, except in the matter of the spacing, which is one of forty-eight