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An instrument was developed to measure the effects of a desensitization program on hand hypersensitivity. It was standardized with 40 "normal" subjects ages 20 to 40 of both sexes and two ethnic groups. Results showed reliability coefficients ranging from .74 to .82 for the three modalities employed in the test. Analyses of variance of agreement between test and retest scores revealed no significant differences in reliability due to hand used, sex, or ethnicity. It was concluded that the instrument could be used as both a clinical and research tool for the measurement of hand sensitivity.

Tactile hypersensitivity is a common sequela of traumatic hand injury. Vibration is used clinically to reduce this hypersensitivity. The purpose of this study was to determine if vibration has an effect on tactile threshold and if so to determine the duration of that effect. Mean tactile thresholds were determined for 24 healthy adults by means of a pressure aesthesiometer. The experimental group (6 men, 6 women) received 10 minutes of vibration. Mean tactile thresholds were redetermined at the end of the 10-minute treatment period in the experimental group and after a 10-minute rest period in the control group (6 men, 6 women). Thresholds were also redetermined at 5-minute intervals for the next 20 minutes in all subjects. The experimental group showed a significant change in mean tactile threshold after 10 minutes of vibration (p less than .001). This difference remained at 5 (p less than .001) and 10 (p less than .05) minutes postvibration but not at 15 and 20 minutes. No significant change in mean tactile threshold was found in the control group. The results indicate that vibration does increase tactile threshold in "normal" hands and the effect lasts for at least 10 minutes. The application of this information to the clinical setting is discussed.

A compact, versatile, and reliable hydrophone preamplifier designed for use in multiple hydrophone arrays is described. The preamplifier is used in the frequency range 2 to 5000 cps (−3 db points) and has a dynamic range in excess of 80 db. The equivalent electrical self-noise is below that of a sea state 0. One vacuum tube for impedance matching and seven transistors for voltage and power amplification are used in the preamplifiers. A total of up to 5 preamplifiers is contained in a cylinder 6 in. in diameter and 12 in. in length. A large amount of negative feedback is used to insure gain stability. The preamplifiers are designed for use with crystal hydrophones with sensitivities greater than −110 db re 1 v/μbar and capacitances of more than 5000 μμf.

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