Medium BGJ was originally developed by Biggers, Gwatkin and Judah in the early 1960's at the Wistar Institute. Subsequent studies resulted in a modification designated BGJb which has been used for supporting cultures of cartilaginous embryonic bone. An additional modification, developed by Sylvia Fitton-Jackson at Strangeways Laboratory in England, is further enriched over the prior formulae. Additional amino acids and vitamins, and increased buffering capacity conferred by the phosphates in the Fitton-Jackson modification, create conditions that permit calcification and growth of cartilaginous embryonic bone.