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The two preceding papers of this series suggest that the state of the plasmalemmal lipids affects cell adhesion. Plasmalemmal composition was altered by the experimental incorporation of fatty acids into R1 and R2 positions in the phosphatidyl components of the cell surface. In this paper we report that: If the incorporation is of long chain length fatty acids (saturated) cell adhesion rises.If the incorporation is of unsaturated fatty acids cell adhesion falls as the unsaturation increases.Incorporation has to be extensive to produce a large change in adhesion.Changes in adhesion parallel the plasmalemmal incorporation but do not follow the total cell incorporation. Item (4) argues that it is plasmalemmal and not other membrane lipids that are involved in cell adhesion. Item (3) suggests that bulk membrane properties and not some very specific grouping are involved in the effects of lipids on adhesion. The similar extents of incorporation of the various different fatty acids and the negligible amounts of lysophospholipids in the membranes of cells that have incorporated fatty acids argue that the effects are not due to differential accumulations of these lysolipids when incubations are done with different fatty acids. The changes in adhesion cannot be accounted for by changes in surface charge density since the electrophoretic mobility of the cells is unchanged by these incubations. It is suggested that these effects on adhesion due to changes in plasmalemmal lipids can be explained either in terms of the action of intermembrane van der Waals-London (electrodynamic) forces in cell adhesion or of changes in surface fluidity. These alternatives are discussed.

Estimates of the electrical resistivity of lattice vacancies in 99·999% pure lead wires have been made in two ways; firstly from measurements of the equilibrium resistivity between 0°c and the melting point, and secondly from determinations of the quenched-in defect resistivity of specimens rapidly cooled to liquid nitrogen temperatures in an atmosphere of helium. The precision of the equilibrium resistance measurements is a few parts in 104 and the quenched-in resistivity could be determined to about 1 × 10-10 ohm cm. In the temperature range 0-250°c the resistivity is given within experimental error by the equation:  [image omitted] and the present results join smoothly with existing data below 0°c.Due to the uncertainty in the extrapolated lattice resistivity for T < 250°c and the difficulty of retaining the equilibrium defect concentration in the quenching experiments, the analysis of equilibrium and quenching data gives respectively upper and lower limits for the vacancy resistivity and the energy of formation of a vacancy. The following mean values were obtained, EVf=0·58±0·13 ev and Δev(m.p.)∼5 × 10-8 ohm cm. Using a value for the vacancy concentration at the m.p. of 2 × 10-4 as determined from expansivity and lattice parameter measurements, values for the excess entropy of formation of a vacancy SVf/k=2·6 and of Δev∼2·5 μ ohm cm/at. % vacancies are found. The latter value can only be considered to be a rough estimate.