» Diphtheria Toxin for Schick Test conforms to the regulations of the FDA concerning biologics (650.1 to 650.7) (see Biologics 1041). It is a sterile solution of the diluted, standardized toxic products of growth of the diphtheria bacillus (Corynebacterium diphtheriae) of which the parent toxin contains not less than 400 MLD (minimum lethal doses) per mL or 400,000 MRD (minimum skin reaction doses) per mL in guinea pigs. Its potency is determined in terms of the U.S. Standard Diphtheria Toxin for Schick Test, tested in guinea pigs.