one which is composed of six segments, the last lumbar vertebra assuming the appearance of a sacral segment; or one which is composed of but four segments, the first sacral being free and having the characteristics of a lumbar vertebra.
Health4All
one which is composed of six segments, the last lumbar vertebra assuming the appearance of a sacral segment; or one which is composed of but four segments, the first sacral being free and having the characteristics of a lumbar vertebra.