distinguish between part_of and containment/located in

[cmungall]

example from TerryM: spleen part_of body cavity

[tmeehan]

Chris added this on my behalf. My issue: In CL, there are cell-types that are part_of spleen. Reasoner infers that cell-types are part_of immaterial anatomical entity. Also, develops_from is transitive over the part_of relationship. Reasoner infers some cell-types as developing_from both material anatomical entity (spleen) and immaterial anatomical entity (body cavity).