  A braided bialgebra is called primitively generated if it is generated as an
algebra by its space of primitive elements. We prove that any primitively
generated braided bialgebra is isomorphic to the universal enveloping algebra
of its infinitesimal braided Lie algebra, notions hereby introduced. This
result can be regarded as a Milnor-Moore type theorem for primitively generated
braided bialgebras and leads to the introduction of a concept of braided Lie
algebra for an arbitrary braided vector space.
