Studies to determine the biological significance of the vitamins.

Abstract

Earlier authors have fully appreciated that conditions other than food and oxygen are necessary for an active growth of cells in the body. This fact is well exemplified in the work of Morgan 1 on the regeneration of the legs of salamanders. Morgan noted that the legs of these animals regenerate as rapidly in starved as in well fed animals. I have sought these other conditions by means of the tissue culture, and find they are a crowding of the cells and stagnation. Single isolated cells or small groups of cells will not grow in a drop of plasma. For these cells to grow they must be crowded with other cells to form a compact mass of considerable size, and be placed in a small amount of stagnant medium so that the loss of soluble materials from the mass is reduced to a minimum. In the presence of oxygen the cells in such a mass begin to grow after a given latent period. 2

In analyzing these factors of cell crowding, stagnation, oxygen and latent period more carefully, I have further found that they signify that growth depends on the accumulation of a certain concentration of an oxydative product of these cells. This product can be readily extracted with salt solution, and when added in a certain concentration to a drop of plasma it will stimulate growth in isolated cells placed in the mixture. In lower concentrations (S₂) it stimulates these cells to migrate and store proteins and fats. Only in certain high concentrations (S₃) can the cells digest these proteins and fats and grow. In all higher concentrations (S₄) it leads to the digestion of the protoplasm of the cells themselves.