THE DIFFERENTIATION AND KERATINIZATION OF EPITHELIUM IN VITRO.

The organization, or, according to Drew, differentiation, of epithelial cells grown in vitro is not due to a specific influence of the associated connective tissue. It occurs in all old pure cultures of epithelium, when the tissue fragment becomes thick and suffers from lack of oxygen and nourishment. Under the same circumstances, keratinization occurs in cultures of epithelium.