a salt solution usually used in combination with naturally occurring body substances (e.g., blood serum, tissue extracts) and/or more complex chemically defined nutritive solutions for culturing animal cells; two variations contain CaCl2, MgSO4·7H2O, KCl, KH2PO4, NaHCO3, NaCl, Na2HPO4·2H2O, and d-glucose.