RESUMO
The present hypothesis for the growth of the epidermis in humans postulates that the cells of the basals layer undergo mitosis and thence migration. This hypothesis has repeatedly been tested against experimental animals using titrated thymidine. In the first instance in human skin there is still no evidence available to show which of, or if all, basal cells undergo mitosis. There is also no scientific evidence to support the hypothesis that individual cells of the basal layer migrate and in the process of migration not only undergo translocations but radical transformation. This has been an assumption which is still faithfully taught as a basic fact. In the second instance there is now ample evidence in man to show, beyond any doubt, that radioactive thymidine has other well recognised metabolic pathways apart from the postulated incorporation into the D.N.A. of pre-mitotic cells. It is also apparent that radioautographs are inconclusive when it comes to equating possible mitotic rates with actual skin growth. The vital, balanced, process of normal keratinisation, studied as it can be at ultrastructural levels, gives evidence of providing a more reasonable basis on which to attempt to clarify the phenomena of growth in epidermis, particularly when it comes to explaining the possible mechanism of formation of the constituent parts of the epidermis between stratum granulosum and fresh air; an area no one has yet succeeded in labelling with tritium (AU)
