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BEFORE commencing the study of malarial blood it is advisable for the beginner to familiarize himself with the microscopical appearances of normal blood, both in fresh and stained preparations. He should learn to recognize the several varieties of leucocyte; to appreciate differences in colour, size, and shape of the red cells; to recognize dirt, vacuoles, forms of crenation, and artificially produced appearances. By mastering such details at the outset important sources of fallacy will be avoided, and in the process of self-education a useful knowledge of technique will be acquired.

For a thorough appreciation of the principles on which blood examinations for the demonstration and study of the malaria parasite should be conducted, it must be borne in mind that the parasite is intracorpuscular. To see it, therefore, it is necessary, particularly for the beginner, so to dispose the corpuscles in the preparations that a proportion of them shall lie flat on the slide, in a single layer, and presenting their surfaces, and not their edges, to the observer (Fig. 16). It is mainly from ignoring this fundamental principle that so many fail to find the parasite.

Preparation of fluid blood films.—To secure this disposition of corpuscles in fresh blood the following procedure, the smallest details of which must be scrupulously carried out, is recommended:— Thoroughly cleanse with alcohol three or four thin cover-glasses and as many slips, and cover them immediately with some convenient vessel so as to protect them from the minutest particle of floating dust. Cleanse one of the patient's finger-tips with alcohol and dry it. Prick the part with a clean needle, and wipe away the first drop of blood that