This principle, common to all animals, is bhe spontaneous impulse by which they perform certain actions. Under this term should be distinguished the instinctive faculty, which Leads the duckling, untaught, into the water, and the chicken, equally untaught, to avoid bhe water: the bird to fly, a child to try to walk; and the instinctive motion, such as the involuntary action of the muscles, as in laughter for pleasure tears for grief, the act 3f swallowing, and the methods of locomotion in the various forms of animal life.