Reaction

(re-ak'-shun). I. Mutual action; interaction. The response of an organ, ti ue, or the system, to a stimulus, agent, or influence. Recuperation or return of power after depre ion or " shock." The supervention of fever after a surgical operation, or trauma. 2. In chemistry, the result of introducing a reagent or tests See Tests, Table of. 3. In electro therapeutics, the muscular contraction following the making or breaking of the current. R., Acid, the reddening of blue litmus paper by the action of an acid; a test for the presence of acids. R., Adamkiewicz's, a reaction employed as a test for albuminoids. See Tests, Table of. R., Alkaline, a reaction indicative of alkaline properties, and in which red litmus paper is changed to blue. R., Amphicroitic, R., Amphigenous, R., Amphoteric, a double reaction occurring occasionally in urine, owing to the presence of substances by which the liquid re sponds to both the acid and alkaline tests. R., Biuret. See Tests, Table of. R. of Degeneration ("/A.A'." diminution and lo of faradic excitability in both m and muscles, the galvanic excitability of the muscles remaining unimpaired, sometimes notably increased, and always undergoing definite qualitative modific; I It is due to a degenerative atrophy in the nerves and muscles, eventually in the muscles only, whose origin is always nervous, paralytic, or atrophic, and whose s in the peripheral nerves, motor roots, or central grav substance. Strict cerebral disease is excluded. The lesion is either in the peripheral nerves or spinal cord. De. R. is of special value in prognosis. "When there is only Partial De. R. slight diminution oi galvanic and faradic excitability, " a le maximum contraction rather than a later minimum "),the di will probably last one or two months; if complete, it will last much longer. The De. R. embraces the following modifications of irritability: 1. Disappearance or diminution of nervous irritability to both galvanic and faradic currents. 2. Disappearance of faradic and increase of galvanic irritability of muscles, generally a ociated with an increase of mechanical irritability. of faradic and increase of galvanic muscular irritability, a ociated generally with increased mechanical irritability. 4. Tardy, delayed contraction of muscles, instead of the quick reaction of normal muscles. 5. Marked modification of normal sequence of contraction. A special variety of the De. R.