If ever a material seemed ill suited for standardization, it is endotoxin. As a standard it has been domesticated, but not entirely tamed; captured from the wild, grown up in captivity on rich media; chemically groomed (by solvent extraction), and trained to behave in a somewhat civilized manner in modern assays. But, still it prances like a caged lion, back and forth, unable to escape its dual ampiphilic nature; unable to decide on the direction it should go in aqueous solution.