Life-source

Every branch vigorously growing on the main stem drawing fecundity from the sap produces leaves, flowers and fruit, but every branch which either from accident, sickness, or refusal to draw from the parent stem. separates itself from the inherited life-source, dooms itself to wither and die.

Source: wiktionary

Because I cut the bonds of those so joined, I bear my head cut off from its life-source, which is back there, alas, within its trunk.

Source: wiktionary

In popular belief, the soul has been seen as the life-source that gives shape, individuality and life to each human being;

Source: wiktionary