It is common experience that pain sensibility in the skin is not a uniform function. Exploration of a small area of the skin with a fine needle will reveal both highly sensitive spots and areas where pain is scarcely or not at all perceived. This variability has been repeatedly commented upon in major studies of cutaneous sensation.1-7 A matter of some practical significance to the clinician, it has not been systematically examined in a quantitative way, particularly with reference to differences among individuals. Such an investigation is here reported.
A calibrated needle algesimeter with a 25-gauge piano-wire spring was used for obtaining pain thresholds (Fig. 1). A 24-gauge hypodermic needle with the hub removed was fastened to the piston in the barrel. The sharpness of the point was checked periodically under the microscope by a comparison with a standard. For the purposes of this study the algesimeter scale was