Page:The American Journal of Psychology Volume 1.djvu/78

 DERMAL SENSITIVENESS TO GRADUAL PRES- SURE CHANGES.

BY G. STANLEY HALL AND YUZERO MOTORA.

17/de 6oKu ^tjtovcl <paveloi}ai. avarrj 7r6repov ev nolv dca^ipovai yiyverai /ud/^ov i] bliyov ;

'Ev roig bliyov.

'Alia ye dfj Kara a/uiKpov uErajSaivuv fiaTJiOv lijauq fMuv em kvavriov y Kara fieya.

Hug 6' ov ; Phaedrus.

Stallbaum, ed. IV, p. 160.

Fontana observed that when a very slight pressure was applied directly to an excised motor nerve it might be made to increase so gradually as to crush the nerve without causing its muscle to contract. Af anasiefT and Rosenthal found also that temperature might be increased and decreased so gradually as to kill a motor nerve trunk without stimulating it. Hit- ter and others since have found that the electric cur- rent has no effect if the density of the current is made to vary slowly enough. Heinzman 1 undertook a more serious experimental solution of the question whether a thermal stimulus could increase so gradu- ally as to be unobserved by the sensory nerves so that death would finally supervene without any movement of either resistance or escape on the part of the animal. Frogs were heated (a) locally with a leg in water gradually warmed, and (b) totally by sitting on a cork floating in a cylinder of water, though it was much harder to boil intact and normal than brained or reflex frogs without sensation enough to cause motion. Their sensory seemed to

x Weber die Wirkung sehr allmaliger Aenderungen thermischer Keitze auf die Empfindungesnerven. Archiv fur die gesammte Physiologie. Bd. VI (1872) S. 222.