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While studying the specificity of opsonins last summer in Professor Wright's laboratory I sought for a method of quickly separating organisms from the liquid in which they are suspended, centrifugating alone requiring from thirty minutes to one hour. The following device was used with splendid success: A constriction (A) is made in a piece of small-caliber glass tubing; the tubing is then bent on itself (B), terminating in an opening (C). Moist filter paper fiber (D) (conveniently made by scraping filter paper with the edge of a knife) is placed against the constriction and packed firmly. Into the long arm is placed the liquid (E) to be filtered and the device is placed in the centrifuge.
Working with staphylococci, I obtained practically bacteria-free filtrates (F) in ten to fifteen minutes from thick suspensions of staphylococci in normal sera. The filtrates showed scarcely any opsonin, and stained specimens practically no organisms.
POTTENGER JE. A CONVENIENT METHOD OF OBTAINING CLUMP-FREE EMULSION FOR OPSONIC WORK.. JAMA. 1907;XLVIII(15):1269. doi:10.1001/jama.1907.25220410045002g