[Ontogenesis of the human fetal nails. I. Observations using the scanning electron microscope]

The development of the nail apparatus of the human foetuses from 6th to 18th weeks of pregnancy, was studied by Scanning Electron Microscopy. The main results can be summarized as follows: 1) first structure to appear is nail field defined by continuous shallow grooves; 2) the shape of the nail field is firstly ovoidal and it extends beyond the tip of the finger; later it becomes flat as in the adult nail plate; 3) the globular blebs of periderm cells accumulate mostly in the tip of the finger; 4) the surface of the nail field is first uniform, then it becomes irregular for the increasing of the process of keratinization.