Abstract
It has been found 1 that eosin, an acidophilic dye, is taken up by a fat mixture containing an oil soluble base, while a basophilic dye, methylene blue, dissolves in a fat mixture with an oil soluble acid. The fat mixture with a base is electrically negative against the mixture with an acid.
Considering the general character of these findings, it seems probable that the same conditions hold also in tissues; hence our model experiments are suitable for explaining that relation of stainability to electromotive forces which has thus far been found in tissues. To corroborate this finding we have performed the following comparative experiments. Forty-three different dyes were used for testing the differential stainability of artificial mixtures such as those mentioned which contain either oleic acid or an amine, and this was compared with the stainability of white blood cells. It was found in each case that a dye which was taken up, exclusively or preferably, by a non-aqueous solution of a higher fatty acid, produced a differential stain on the nucleus of white blood cells. On the other hand, any dye with a preference for a mixture containing a fat soluble base preferably stains the cytoplasm and leaves the nucleus unstained, or but slightly stained.
Many nuclear stains like methylene blue are water-insoluble bases. Evidently, they are taken up by a solution of oleic acid in a suitable solvent, forming, e. g., methylene blue oleate, which is oil-soluble and hence stains. However, there are also nuclear stains which are not bases, e. g., hematoxylin, a widely used nuclear stain which has all the characteristics of an acid. It was of special importance to test the type of oil solubility in this case.
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