Spon`ta*ne"i*ty (?), n.; pl.
Spontaneities (#). [Cf. F.
spontanéité.] 1. The quality
or state of being spontaneous, or acting from native feeling,
proneness, or temperament, without constraint or external
force.
Romney Leigh, who lives by diagrams,
And crosses not the spontaneities
Of all his individual, personal life
With formal universals.
Mrs. Browning.
2. (Biol.) (a) The
tendency to undergo change, characteristic of both animal and
vegetable organisms, and not restrained or cheked by the
environment. (b) The tendency to activity
of muscular tissue, including the voluntary muscles, when in a state
of healthful vigor and refreshment.