Ueber die Fldehenempfindung in der Haut

REvies the article "Ueber die Fldehenempfindung in der Haut" by Helen B. Thompson and Katharing Sakijewa (Zeitschrift fur Psychologie und Physiologie der Sinnesorgane, December, 1901, XXVII. Pp. 187-199). This article reports a study of judgments of the size of surfaces touching the skin, and the influence of pressure on these judgments. The experiments have the merit of simplicity, and the observations are interesting and valuable. The apparatus consisted of pieces of cork of different sizes attached to an instrument for measuring the pressure. With these the discriminating power of different parts of the body was investigated. The pressures used were 20, 70, 100, 150, and 250 gm. It was observed that few judgments were purely judgments of size. The subjects who knew that the pressures of any two surfaces to be compared were always equal were likely to base their judgments on the subjective feeling of difference in pressure. On parts where the tissue beneath the skin is soft it is difficult to tell just what are the chief factors. The smaller surface sinks deeper and this seems to aid in judging. Where the bones are close to the skin the judgment is in the highest degree based on surface sensation. This is probably because the edges are felt more plainly here than on soft tissue. Changes of pressure between 20 and 250 gm. make but little difference so long as the pressures of the two surfaces to be compared remain equal. The discriminating ability of all parts of the skin not trained in touch is about the same.