Studies on cancer. II. The significance of the effect of circulation on the growth of cells.

Abstract

As early as 1913 1 , 2 I had already shown that the growth and migration of fixed tissue cells is proportional at all times to the size of the fragment, the cell density of the fragment and indirectly proportional to the thickness of the layer of the medium. All of these proportions hold, however, only to the limits of an active oxygen diffusion to all parts of the culture. Oxygen, as I have pointed out, diffuses readily only 0.5 to 0.7 mm. into clots and later I have found that it diffuses readily no greater than 1 mm. into many dense fragments of tissue. For any of these fixed tissues the maximum activity of the cell is seen about fragments 1 mm. in diameter planted in layers of medium 0.5 mm. in thickness.

Single cells cannot grow in the plasmatic medium of the culture. Connective tissue and mesenchyme cells may stretch out to take their characteristic shapes and migrate short distances. These cells will not grow. Active migration is always proportional to the size of the fragment up to the limits cited above. In the primary plasma cultures an active growth of the mesenchyme cells is seen only about the cellular fragments of the tissues of young embryos and malignant tumors. The cells from these fragments suffer not only this active growth reaction but they later suffer frequently a complete degeneration in the cultures.

This degeneration as it is seen in these active growing cells is peculiar to all of the cultures, It commences early in the centers of all fragments except the least cellular ones cut from scars and adult subcutaneous tissue. It spreads outwards from this center. In the cultures of the more cellular tissues it involves sooner or later all the cells except those which migrate directly into the plasmatic medium and out of the line of diffusion of substances from the fragment along the surface of the medium.