Cancer Cell and Growth-Regulating System of the Body

Abstract

A FRAGMENT of tissue removed from the body and explanted in vitro does not commence growing immediately. A certain period of time must elapse before proliferation sets in. In a paper some years ago which has been overlooked in the literature on tissue culture, Cohn and Murray¹ reported that the period between the moment that the tissue fragment is explanted in vitro and the first appearance of new cells varies with the age of the embryo. As the embryo develops, this latent period becomes progressively longer. The latent period of adult tissue explanted in vitro is considerable as compared to that of embryonic tissue. We have demonstrated² that it is approximately three times longer than that of tissue taken from an embryo in a late developmental stage. Furthermore, we have shown that during postnatal growth the latent period increases gradually³. It reaches its maximum when the animal ceases growing and remains constant thereafter, not even changing during senescence^3,4.