Abstract
Histospectrography, as developed by Policard, 1 and by Gerlach and Gerlach, 2 is a method of examining the elements in tissues which consists of passing a high frequency spark through a predetermined area in a section of tissue and by means of the spectrograph analyzing the rays emitted. The spectrograms will contain the lines characteristic of the elements encountered by the spark in passing through the tissue. It has been pointed out by Policard 1 and Gerlach and Gerlach 2 that one of the greatest difficulties encountered is the selection of electrodes; not only do the characteristic lines of the major element of the electrodes appear on the spectrum, but also those of even small impurities in the metal. In the course of our experiments with the technique, a means was devised whereby the purity of the electrodes is rendered immaterial, and the choice of basic metal almost so. In fact, for all practical purposes, our spectrograms contain lines characteristic only of the tissue.
The tissue support assembly differs entirely from that employed by other investigators. Policard supports tissue sections for analysis on a metal plate, which forms the lower electrode of the spark gap, carried by a special mechanical stage to permit the selection of the area to be sparked while it is under observation with a microscope. The upper electrode is a metal point immediately above the tissue. Gerlach and Gerlach's apparatus differs from Policard's in that a glass plate is interposed between the specimen and the base plate. With both procedures the possible area of localization is of the order of 1 mm. in diameter and lines are photographed from one or both electrodes.
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