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) .
The second social level of age groups is the microsocial, that of small groups, most notably the family. Here generation refers to ranked descent within a lineage, and here the term is least ambiguous: mothers and daughters, grandmothers and granddaughters, great-grandmothers, etc.