Re*ac"tion, n. (Psycophysics)
A regular or characteristic response to a stimulation of the
nerves.
{ Wi*dal's", or Wi*dal", test or
reaction } (?). [After Fernand Widal (b. 1862),
French physician.] (Med.) A test for typhoid fever based
on the fact that blood serum of one affected, in a bouillon culture of
typhoid bacilli, causes the bacilli to agglutinate and lose their
motility.
Re*ac"tion (r&esl;*ăk"shŭn),
n. [Cf. F. réaction.]
1. Any action in resisting other action or force;
counter tendency; movement in a contrary direction; reverse
action.
2. (Chem.) The mutual or reciprocal
action of chemical agents upon each other, or the action upon such
chemical agents of some form of energy, as heat, light, or
electricity, resulting in a chemical change in one or more of these
agents, with the production of new compounds or the manifestation of
distinctive characters. See Blowpipe reaction, Flame
reaction, under Blowpipe, and Flame.
3. (Med.) An action induced by vital
resistance to some other action; depression or exhaustion of vital
force consequent on overexertion or overstimulation; heightened
activity and overaction succeeding depression or shock.
4. (Mech.) The force which a body
subjected to the action of a force from another body exerts upon the
latter body in the opposite direction.
Reaction is always equal and opposite to action,
that is to say, the actions of two bodies upon each other are always
equal and in opposite directions.
Sir I. Newton (3d
Law of Motion).
5. (Politics) Backward tendency or
movement after revolution, reform, or great progress in any
direction.
The new king had, at the very moment at which his fame
and fortune reached the highest point, predicted the coming
reaction.
Macaulay.
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
centrally, escapes at its periphery in a direction opposed to that of
its motion by orifices at right angles, or inclined, to its
radii.
Re*ac"tion, n. (Psycophysics)
A regular or characteristic response to a stimulation of the
nerves.
{ Wi*dal's", or Wi*dal", test or
reaction } (?). [After Fernand Widal (b. 1862),
French physician.] (Med.) A test for typhoid fever based
on the fact that blood serum of one affected, in a bouillon culture of
typhoid bacilli, causes the bacilli to agglutinate and lose their
motility.
