Thioglycollate Medium, Brewer is used to detect the presence of bacteria in normally sterile materials. Casein Digest of Peptone, Beef Extract, and Soy Peptone provide amino acids, peptides, carbohydrates, vitamins, and minerals. Dextrose is the fermentable carbohydrate. Sodium Chloride maintains the osmotic equilibrium. Sodium Thyoglycollate lowers the oxidation-reduction potential of the medium and thus prevents the accumulation of toxic peroxides. Its sulfhydryl groups also neutralize the antibacterial effect of mercurial preservatives. Methylene Blue serves as an indicator of oxidation-reduction. 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.