“…Data presented by Schaefer et al (1955) suggested that fractions from streptomycin and penicillin fermentation processes contain unidentified growth factor (UGF) activity similar to that found in fish meal arid distillation solubles plus possibly an additional factor. In this respect, penicillin mycelium residue appeared to be qualitatively comparable to fish solubles as a source of the chick growth factor(s), according to Edwards eta!.…”