On the Dialysability of the Growth-activating Principle Contained in Extracts of Embryonic Tissues

These experiments appear to indicate that whatever substance in embryonic tissue extracts excites mitosis, and therefore would appear to be the growth-stimulating substance, is capable of passing through a collodion membrane which is impermeable to proteins, at all events in such concentration as would give rise to any biuret reaction. The substance is therefore diffusible.