Calcium, Magnesium, and Local Anesthesia

5 ml aliquots of chloroform: methanol (2:1) containing 5 mg of cephalin (animal)/ml w e r e agitated for 10 rain with 2.0 ml aqueous solution containing NaC1 116 n~ , KCI 2.5 raM, CaCI2 1.5 m.~, and MgC12 in concentrations ranging from 0.7 up to 16 mM at pH 6.0. After centrifugation and separation of the two phases Ca ++ and Mg ++ concentrations were determined in the upper (water -b methanol) layer. Experiments in which cephalin was substituted by extracted lipids (uterus, brain) and MgCls substituted by MgSO4 have given similar results.