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mething that rouses the mind or spirits; an incentive; as, the hope of gain is a powerful stimulus to labor and action.

The positive or negative stimulus exerted by oxygen on aërobic and anaërobic bacteria. -- A`ër*o*tac"tic (#), a.

A sensation or sense impression following the removal of a stimulus producing a primary sensation, and reproducing the primary sensation in positive, negative, or complementary form. The aftersensation may be continuous with the primary sensation or follow it after an interval.

One who, or that which, brings forth, elicits, or extracts. Stimulus must be called an eductor of vital ether. E. Darwin.

t proportions; different; -- opposed to homologous; as, heterologous organs. Heterologous stimulus. (Physiol.) See under Stimulus. -- Heterologous tumor (Med.), a tumor differing in structure from the normal tissues of the body.

ation; esp., the property which living muscle processes, of responding either to a direct stimulus of its substance, or to the stimulating influence of its nerve fibers, the response being indicated by a change of form, or contraction; contractility.

of the Jacobins; violent and factious opposition to legitimate government. Under this new stimulus, Burn's previous Jacobitism passed towards the opposite, but not very distant, extreme of Jacobinism. J. C. Shairp.

The special properties and functions of the nerves; that capacity for transmitting a stimulus which belongs to nerves. G. H. Lewes.

ely rapid growth of the upper surface of dorsiventral organs, such as leaves, through the stimulus of exposure to light. Encyc. Brit.

ments of plants and their organs; the study of the phenomena of curvatures induced by the stimulus of light. --Pho`to*dy*nam"ic (#), Pho`to*dy*nam"ic*al (#), a.

Incitement; stimulus; as, provocation to mirth.

Reaction time (Physiol.), in nerve physiology, the interval between the application of a stimulus to an end organ of sense and the reaction or resulting movement; -- called also physiological time. -- Reaction wheel (Mech.), a water wheel driven by the reaction of water, usually one in which the water, entering it ce…

Of, pertaining to, or produced by, stimulus or excitation without the necessary intervention of consciousness. Reflex action (Physiol.), any action performed involuntarily in consequence of an impulse or impression transmitted along afferent nerves to a nerve center, from which it is reflected to an efferent nerve, and…

consciousness, whether agreeable or disagreeable, produced either by an external object (stimulus), or by some change in the internal state of the body. Perception is only a special kind of knowledge, and sensation a special kind of feeling. . . . Knowledge and feeling, perception and sensation, though always coexiste…