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Article
April 23, 1904

A METHOD OF MICROSCOPIC OBSERVATION BY MEANS OF LATERAL ILLUMINATION.

Author Affiliations

CHICAGO. (From the Pathological Laboratory of Rush Medical College.)

JAMA. 1904;XLII(17):1075-1078. doi:10.1001/jama.1904.92490620017001g
Abstract

INTRODUCTION.  Last year two German physicists, Siedentopf and Zsigmondy, published an article1 in which they described an apparatus for the observation of ultramicroscopic particles. The object which they selected for examination consisted of a piece of glass through which was diffused uniformly particles of metallic gold in a very fine state of division. By means of a powerful light— either the sun or an electric arc—passed through a complicated system of condensers, a very small but exceedingly intense focus of illumination was obtained. The piece of glass containing the gold was placed in this focus so that the light entered the glass from the side. It was then observed with an ordinary microscope from above. By this arrangement none of the light entered the microscope directly. To the naked eye, or with the ordinary microscope, the glass appeared perfectly homogeneous. But by this special illumination the individual particles of

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