FOUR FIGURESEven a casual inspection of the palmar and plantar surfaces suffices to demonstrate that there are regional variations in the breadths of epidermal ridges. Ridges of the sole are generally coarser than those of the hand (Galton, 1892) ; variations in different regions are apparent in the hand and foot alike, the prominent distinction being increased ridge breadth in the proximal territories. When corresponding regions of different individuals are compared it is observed that ridges tend to be coarser in men than in women, that they coarsen in prenatal and postnatal growth, and that some differences occur among individuals of the same sex and body size. Curiously enough, the literature contains little more than casual statements on the subject of ridge breadth, most often presented as in this brief introductory comment without quantitative data.The most extensive available information relates to the growth of ridges : Kolliker (1848-1849), Kollmann (1883), A. F. Hecht ( '24). The findings of these authors are in close agreement, and Hecht 's figures are cited as representative. The following are average breadths of single ridges, in fingertip patterns alone: three premature infants 0.15 mm.; seven newborn infants 0.18 mm. ; then, without giving the numbers of subjects involved, 10 years 0.30-0.35 mm.; adult women 0.40-0.50 mm. ; adult men 0.50 mm. It will be noted that Hecht 127