In addition to parthood relations, containment relations are needed for describing the locations of anatomical individuals. My lungs are contained, but not part of, in my thoracic cavity. Urine is contained in, but not part of, the cavity of my urinary bladder. Ontologies such as the FMA and GALEN use containment relations extensively. However, the FMA's and GALEN's usage of containment relations differs significantly. To provide anatomical ontologies with clear semantics and consistent reasoning strategies, it is necessary to precisely determine the logical properties of their containment relations. In this paper, I define different versions of containment relations in a formal theory and distinguish important logical properties of these relations. The formal containment relations are used to partially analyze and highlight differences between the FMA's and GALEN's containment relations.