(Fig 1). The temperature of the skin, subcutaneous tissue, and muscle (at an aver¬ age depth of 3.5 cm in the brachioradialis muscle group) was determined, using copper constantan thermocouples, while motor conduction velocity of the segments of ulnar and median nerves coursing through the portion of the limb enclosed in the ple¬ thysmograph was measured according to the meth¬ od of Thomas et al8 (Fig 1)

No abstract

Although the use of ultrasound as a therapeutic agent in the field of physical medicine continues to grow, there are still a number of questions concerning its physiologic effects which remain unanswered. With regard to the thermal response, it is generally accepted that practically the entire amount of energy applied to the tissues through this medium is absorbed and converted into heat. As a result, there is a rise in tissue temperature, most marked in the bones and nerves in which selective heating appears to occur (1-3). The effect of ultrasound on blood flow has been investigated by a number of workers. Bickford and Duff (4) reported that in man, exposure of the forearm to 2 watts per square centimeter produced minor increases in local circulation in one-half the cases and no change in the others, while only with dosages of 3-334 watts was a significant augmentation consistently noted. Paul and Imig (5) performed a similar study and obtained essentially the same results. In the case of dogs, Paul and his associates (5, 6) found 1 watt per square centimeter to be an effective quantity of ultrasonic irradiation for the production of a vascular response. In the present study it was decided to