Pith

The soft spongy substance in the center of the stems of many plants and trees, especially those of the dicotyledonous or exogenous classes. It consists of cellular tissue.

The spongy interior substance of a feather.

The spinal cord; the marrow.

Hence: The which contains the strength of life; the vital or essential part; concentrated force; vigor; strength; importance; as, the speech lacked pith.

To destroy the central nervous system of (an animal, as a frog), as by passing a stout wire or needle up and down the vertebral canal.

the choicest or most essential or most vital part of some idea or experience; "the gist of the prosecutor's argument"; "the heart and soul of the Republican Party"; "the nub of the story"

soft spongelike central cylinder of the stems of most flowering plants