Several kinds of recently advanced microanalytical techniques—like electron probe x-ray microanalysis, laser Raman microprobe, and Fourier transform-infrared spectroscopy combined with a microsampling method—have been used for the study of the microstructure of gallstones. The organic and inorganic constituents of three kinds of gallstones are characterized on a microscopic scale. The microstructure of a cholesterol-bilirubin gallstone with a layered structure has been studied with particular emphasis. Small white particles contained in both a bilirubin gallstone and a cholesterol-bilirubin mixed gallstone have been found to consist of calcium salt of a fatty acid, probably calcium palmitate. The results obtained here will be very useful for understanding the mechanism of the gallstone-formation process.

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