Development of dermal ridges in the fetus.

This paper describes a new technique to inspect dermal ridges on the dermal surface instead of the epidermal surface. The dermal surface was exposed by chemical treatment and stained with toluidine blue. Dermal ridges are observable by the metachromatic effect of the reagent, which might suggest a close relationship between morphological characteristics and quantitative variations of biochemical components in the connective tissue. Dermatoglyphic features were recognized in fetuses from the 14th gestational week. Morphogenesis of dermal components--that is, grooves, primary and secondary dermal ridges, furrows, papillae, and sweat ducts--was examined at various gestational stages. The general law in the developmental sequence of the ridges in different volar areas was also confirmed.