Bechterev's Instruments

BECHTEREV'S INSTRUMENTS. Algesthesiometer, an instrument for the precise measurement of pain sensitivity; irritation is produced by a needle ejected from the instrument by a spring; the length of the needle is changed by means of a micrometric screw, as a result of which the degree of irritation is in direct proportion to the length of the needle, i.e., to the depth of its penetration into the tissues. - Baresthesiometer, an instrument for measuring sensitivity to pressure; irritation is produced by a spring pressing on a rod, the end of which, applied to the site of irritation, is fitted with a rubber cap; the degree of pressure is measured in grams and indicated by a clock hand. - Myoesthesiometer, an instrument for investigating muscle sensitivity, i.e., the sensation of pain when muscles are compressed; the instrument is a large compass, at the end of one leg of which a baresthesiometer is fixed; by compressing a muscle (or group of muscles) with this compass, the degree of approximation of the compass legs in centimeters (on the instrument scale) and the amount of pressure in grams (on the baresthesiometer scale) are noted at the moment of sensation of pain. - Osteoacusmeter, an instrument for investigating the sound conductivity of the skull bones; sound from an electric tuning fork, transmitted through the bone, is listened to with the help of a rubber tube. - Seismometer, an instrument for investigating the sense of vibration, allowing the possibility of using tuning forks of various vibrations while eliminating the difference in their pressure on the skin surface. - Trichoesthesiometer, an instrument for investigating hair sensitivity: mechanical irritation of the hairs is produced by a metal plate set in oscillatory motion by electromagnets.