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42 permanent preparations be desired, or should it be inconvenient to make an immediate examination of the blood. Many methods have been devised; here only one or two can be given.

Preparing the film.—It is usual to spread the blood on cover-glasses; for many reasons I prefer to spread it on slips. There are various ways of preparing the films; the following I can recommend:—



Probably the easiest, as well as the quickest and most convenient, is a modification of that recommended by Christophers and Stephens. Prick the cleansed finger-pad or lobe of the ear, and express a droplet of blood. Take this up by touching it lightly with a clean glass slip about an inch from one end of the slip. Across the slip and on the blood lay the shaft of the needle—an ordinary straight, rather long sewing needle (Fig. 19). Pause for several seconds until the blood has run out by capillarity between the needle and the slip; then, holding it by one end, push the needle over the face of the slip in the direction of the length of the latter, so as to spread the blood over the entire breadth of the middle third of the slip. By passing the soiled needle through the lapel of the coat, the operator can cleanse it quickly and be ready to make, by a repetition of the manœuvre, a series of films from the same puncture.