The effect of light on the staining of cells

Former studies of the structural changes in blood cells, especially of the behavior of cell granules under the influence of different external conditions, made it desirable to investigate the behavior of cells in different staining solutions, especially in solutions of vital stains. In the course of various investigations, it was found that solutions not only of eosin but also of other stains, as neutral red, affect the cells very differently in light and in dark. That eosin and other fluorescent substances are much more poisonous for cells and for ferments in light than in dark has been previously shown by von Tappeiner, Raab and a number of others. The results of my investigations which were carried out (partly with the coöperation of Mr. L. P. Shippen) in the summers of 1905 and 1906, the last experiment having been done at the end of August, 1906, may be summarized in the following way:

1. In solutions of dyes (neutral red, eosin, methylene blue, methyl violet and others), cells (eggs of Asterias) are stained differently according to whether the cells and solutions are exposed to the light or kept in the dark.

2. combination of an acid and a basic dye (eosin and methylene blue) increased markedly the differences in the staining of the cells in the light and in the dark, in so far, as a small addition of methylene blue to eosin suffices to increase very much the staining reaction which is characteristic for light. The same holds good, probably, for other combinations, as neutral red and eosin. A mutually neutralizing or antitoxic effect of basic and acid dyes does, therefore, not exist.