RECENTLY, Park and Strominger1 assumed that uridine-diphosphate compounds extracted from cells of Staphylococcus aureus H treated with penicillin are the precursors of the cell wall, because the cell wall and one of their compounds contained muramic acid, alanine, glutamic acid and lysine in the ratio of 1 : 3 : 1 : 1. But the cell wall also contained glycine (ratio 3 : 8).