PEPTONE, PROTEIN HYDROLYSATES, INFUSIONS AND EXTRACTS ARE THE MAJOR SOURCES OF NITROGEN AND VITAMINS IN CULTURE MEDIA. PEPTONES ARE WATER-SOLUBLE INGREDIENTS DERIVED FROM PROTEINS BY HYDROLYSIS OR DIGESTION OF THE SOURCE MATERIAL; E.G., MEAT, MILK, SOYA ETC. PEPTONES ARE DERIVED FROM MEAT DIGESTED BY PROTEOLYTIC DIGESTION.