Effects of Ultrasonic Vibrations on Nerve Tissues.

Abstract

Excised crayfish ventral nerve cords exposed to ultrasound (-35 watts/ sq. cm., frequency 1 mc.) exhibited a reduction of spontaneous activity after several seconds exposure and recovered its original activity about 1 min. after the ultrasound was turned off. Frogs positioned so that ultrasound was incident on the dorsal surface over the lumbar enlargement of the spinal cord exhibited paralysis of the hind legs after 4.3 sec. exposure (at room temp.) and exhibited paralysis after 7.3 sec. exposure (at 1[degree]-2[degree]C). Histological examination of the sciatic nerves showed extensive degeneration of nerves and examination of the spinal cord showed marked pathology of the lower motor neurones. Temp. measurements indicated that crayfish ventral nerve cord exhibited a max. rise of 1[degree]-2[degree]C. The spinal cord of intact frogs exhibited temp. increases of the order of 25[degree]C. By using frogs cooled to 1[degree]C and reducing the ultrasound exposure to two 4.3 sec. pulses interrupted by 4 min. cooling off periods, it was demonstrated that temp. rises did not exceed 15[degree]C and that paralysis of the hind legs occurred during the second 4.3 sec. exposure. It was concluded that the above effects of ultrasound on the systems studied are produced by physical factors other than temp.