1. Gentian violet may be regarded as a true vital nuclear stain.
2. Embryonic and adult tissue of the frog will grow in vitro in the presence of gentian violet of a far stronger dilution than that necessary to kill many bacteria. In these experiments, for example, successful tissue growths were obtained when gentian violet 1 to 20,000 was used, yet Bacillus subtilis will not grow in 1 to 100,000 dilution and grows very badly in 1 to 1,000,000 dilution. This fact may simplify the technique of the growth of certain tissues by eliminating the risk of bacterial contamination.
3. The use of stains in the plasma in which tissue is grown will probably facilitate the study of nuclear growth.
4. Gentian violet appears to have a certain selective action on tissue similar to that exercised by the dye on bacteria. Certain observations made last year in this laboratory (too few to serve as more than a suggestion) seem to indicate that another dye (methylene blue) acted as a stimulant to the growth of connective tissue. These leads should be followed out and the effect of various stains studied in the hope of discovering dyes which will exercise a sharp selective action on growing tissue.
5. The growth of animal cells in a strength of dye much more than sufficient to kill many pathogenic organisms lends encouragement to efforts now being made in this laboratory to apply the observations on the bactericidal effect of gentian violet and allied stains to the treatment of disease. Moreover, the ability of growing cells to rid themselves of this dye would indicate that it may be possible to apply the dye to infected tissue and count on the cells to eliminate the material after its work had been done.