418 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS I Hole for ß I screw mount Vinyl Tab I / I Skin strip glued I::: :! tovinyl tab ! !1' Skin strip i:iiiii?.? Notch for •'VinYi 'Tahiti pendulum hooks Figure /. Mounting of skin strip between vinyl tabs The sections were dried either on a glass microscope slide or between sheets of nonplasticized cellophane held planar between two fiat porous porcelain plates with gentle pressure. The skin sections were next cut into thin strips about 6 mm •( 2 mm, taking care to cut as parallel to the dermatoglyphs as possible. Each strip was then mounted between two vinyl tabs using a cellulose acetate glue (Fig. 1). The glue was applied while the mounting tabs were held in a special clamping device in a planar condition and at a fixed distance apart. The strips were then handled in this chunping device at all times except when measure- ments were being performed on them. The physical properties of these thin keratin strips were then measured by a specially constructed torsional measuring instrument. The ('allus strip mounted between the plastic tabs was hung in a vertical position hy using a screw mount through a hole punched in one of the plastic tabs. A torsion pendulum constructed of soft aluminum wire was next hung onto the bottom plastic tab (Fig. 2). The oscillating torsion pendulum was mounted so as to interrupt a light beam impinging on two banks of silicon B2M solar cells of the self-generating type. The two banks of cell circuits were arranged in a 1)ucking fashion so that no net output from the system was observed when •he pendulum was at rest. As the pendulum was set in motion, it allowed more or less light to impinge on each of the bucking banks of photocells and therel)y set up a continuously varying signal reflecting the excursions of the keratin strip itself (Fig. 3). The output was then fed into a milli- volt chart strip recorder. The results gave a modified sine wave (Fig. 4). The relative humidity and temperature at which the above measure- ments were made were controlled by having the callus strip portion of

MEASUREMENTS ON SKIN 419 -- Aluminum wire {Total mass of pendulum5.5Le.adgrams} 78 cm Figure 2. Wire pendulum hanging from vinyl tabs Torsion assembly Dual banks of solar cells 10 "•:':':•• © Direction of motion "Ze!o" *Recorder input Figure 3. Electronics of motion detection system amplitude Start pendulum in motion P: period Figure 4. Typical curve traced by recorder from torsion pendulum apparatus