Abstract
Technique and theory of a simple method for study of certain physical chemical properties of the surfaces of bacterial and other cells have been reported. 1 In its present development the method is chiefly useful for examination of cells or other test objects in whose surface lipins are present or suspected, and whose range of size is from that of a bacterium to that of a large white blood cell. It is hoped that other workers will extend and adapt it to their purposes in the study of permeability, cytolysis, action of protective colloids and other problems.
The present report concerns the serum sensitization of acid-fast bacteria. These are tested as follows:
A drop of oil (Tricaprylin, Kahlbaum) and a drop of bacterial suspension are placed upon a carefully cleaned slide. A clean cover slip is placed on them in such a way as to spread the oil into a film under one end of the cover slip, and the watery suspension into a film adjoining the oil. The preparation is then studied under the dark-field microscope. The oil-water boundary surface or interface appears as a bright line, and the bacteria as bright shimmering objects against a dark background. If the preparation has been properly made the oil encroaches slowly on the aqueous phase so that the interface moves across the field and overtakes the sedimented or suspended bacteria and bacterial clumps.
The behavior of the bacteria when overtaken by the interface differs according as their surface is physico-chemically 2 similar to and therefore miscible with the oil or with the water. Normal acid-fast bacteria when touched by the oil are shot violently into the oil phase. If in clumps, the bacteria are dispersed explosively by the interfacial stresses and the scattered bacteria suddenly appear in the oil phase.
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