A sensitive technic for frequency analysis of the first heart sound (Sl) during isovolumic contraction time (ICT) was developed. Recorded heart sounds were filtered with a dynamic analyzer. Amplitudes of frequencies between 30 and 70 cps were plotted as a percentage of peak total energy of S, against frequency. A consistent and reproducible frequency "fingerprint" was obtained in 74 normal subjects. Frequencies of S, were shown to be directly proportional to ventricular elasticity (VE) and inversely proportional to combined ventricular mass (VM). VM is constant during ICT. Amplitude at 40 cps was less than at 30 cps because of

A study has been made of the molecular and crystallographic structures of Langmuir-Blodgett multilayer films of lead stearate. Electron microscopy and diffraction were used in the examination of such a film which had separated from the glass slide on which it had been formed. The films consist of a large number of three-dimensionally ordered lead stearate crystals arranged in near-perfect alignment, with the longest axes of their unit cell projecting from the plane of the supporting substrate. The unit cell of the lead stearate crystal is either monoclinic with the space group P21/a or orthorhombic with the space group P21212. The former is considered to be rather the more likely. The major lattice spacings are 4.96/~ (100), 7.38/~ (010) and 47 ~ (001). The/~ angle of the monoclinic unit cell is not known but is probably within a few degrees of 90 °. The lead atoms are in special positions in the basal plane, regardless of which is the correct unit cell, and the hydrocarbon chains make an angle of 62 + 5 ° with the basal plane. Any free stearic acid in the films occurs as a separate phase.

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