Introduction
Previous work reported on the histopathology of high-intensity focused ultrasound on the central nervous system of experimental animals has been carried out at a frequency of 980 kc. using a multibeam transducer,1-3 or at 835 kc. using a focused beam.4 The present communication deals with the minute structural changes in the spinal cords of mice irradiated at a frequency of 2.5 mc. with a focused beam. Details of the method and dosage have already been reported.5
Material and Methods
Adult white mice were irradiated through the intact shaved skin through the prominent hump in the dorsal spine. This lies approximately at the level of the eighth thoracic vertebra. The transducer cone was filled with degassed isotonic saline and covered with goldbeater's skin; this allows the saline solution to permeate slowly and so ensures a liquid contact between the transducer and the experimental animal through which the