A mixture of phosphatidylglycerols isolated from egg; a metabolic precursor of cardiolipin; a constituent of plant, animal, and bacterial cell membranes; species containing polyunsaturated and monounsaturated fatty acyl chains inhibit and promote proliferation of murine keratinocytes, respectively; is the second largest lipid component of mammalian lung surfactant, comprising 10% of the lipids; levels are decreased in the lung surfactant of infants with respiratory distress syndrome