Intracellular hydrion concentration studies. V.-Colorimetric p H of malignant cells in tissue culture

The microinjection of the relatively small of mammalian tissues offers considerable difficulties, the chief of which is some means of knowing whether the cell in still alive after the injection. Usually deterioration of the cell is made evident by easily recognisable morphological changes, but this is not always the case. The best criterion so far encountered for the injection of solutions of dyes is the restriction of the color to the cell injection. This is more difficult to judge with dyes, especially those basic in nature, which easily penetrate cells from without. In such cases special pains must be taken to prevent spilling into the medium during the time that the pipette is being brought into the cell to be injected. Fortunately, the Clark and Lubs indicators are sodium salts of acid dyes, and most of these penetrate living cells, either very slowly or not at all. The consequence is that a small amount accidentally spilled about the cells quickly fades away by diffusion into the surrounding medium and does not disturb the procedure of injection. When once a solution of an acid dye is injected into a cell, the acquired colour persists for an appreciable length of time. Up to the present, the injection of cells of somatic tissues has always been followed, generally within 5 to 15 minutes, by observable signs of cytolysis. This is accompanied, and frequently preceded, by a fading out of the colour of the injected dye. From these observations it has been assumed that the cell is alive as long as the indicator is still within the cell injected. This assumption is supported by experiments on marine ova (Needham, 1926), for they have been demonstrated to be alive while retaining the colour of the injected indicator both in the cytoplasm and in the nucleus (Chambers and Pollack, 1927).