Effects of ultra-violet rays upon skeletal muscle

Abstract

A frog sartorius muscle was suspended in tyrode solution and exposed to ultraviolet on both sides. The exposure causes contraction after a few minutes and slow relaxation after the exposure. The presence of Ca ions is necessary for the contraction; K and Mg ions seem to moderate its action. The excitability of the muscle to electric shock becomes less and less during exposure as contracture or "light rigor" develops. The contracture passes off but can not be produced again by a 2nd exposure.