Vulcan blood is presumed to be green in color , the explanation for this ( first definitely advanced in the installment  Obsession ,  from the original program ) being that the oxiferous ( oxygen-carrying ) protein hemoglobin , in Vulcan blood cells , is chemically based on the element copper , rather than the element iron as is the case with ...
SECONDARY GROUPS The term secondary group has come into use in sociology to describe any group which lacks one or more of the elements that go together to characterize a primary group. In general, a secondary group is composed of individuals who lacks strong emotional ties one another.. (end of quotation) .
People in a secondary group interact on a less personal level than in a primary group. Rather than having as the goal the maintenance and development of the relationships themselves, these groups generally come together to accomplish a specific purpose.