Abstract
A number of very important compounds that are found in both plants and animals contain a cyclo-pentanoperhydrophenanthrene carbon skeleton as part of their molecules. These compounds, commonly grouped under the heading "steroids", include the sterols, the bile acids, the sex hormones, the adrenal cortical hormones, the cardiac aglycones, and the D-vitamins.|The steroids differ from one another in the arrangement of double bonds in the rings, angular methyl groups, the presence of oxygen, hydroxyl, or other groups, and, in certain cases, there may be a break in one of the rings.