Thioglycollate Medium without Indicator is used to cultivate and detect a variety of microorganisms, especially obligate anaerobes, in normally sterile materials. Enzymatic Digests of Casein and Soybean provide nitrogenous sources. Dextrose is the fermentable carbohydrate. Sodium Chloride maintains the osmotic equilibrium. Sodium Thyoglycollate and L-Cystine lower to oxidation-reduction potential of the medium and thus prevent the accumulation of toxic peroxides. Their sulfhydryl groups also neutralize the antibacterial effect of mercurial preservatives. By retarding the dispersion of CO2 and the diffusion of O2 and reducing substances, Agar eliminates the need for seals and allows for the growth of anaerobes.