. The biology of the frog . ovements are in a state of tonic contrac-tion as if these movements were suddenly inhibited. Thebreathing movements and the heart beats are at first accel-erated, but at a later stage their rate falls below the normal(Heubel), and there is a decreased responsiveness to ex-ternal stimuli. Dif-ferent frogs varygreatly as regardsboth the ease withwhich they may behypnotized, and theduration of the hyp-notic state. In somecases if a frog is sim-ply placed on its backwithout being held,it may become hyp-notized after it hasrighted itself a fewtimes, and lie for along tim
. The biology of the frog . ovements are in a state of tonic contrac-tion as if these movements were suddenly inhibited. Thebreathing movements and the heart beats are at first accel-erated, but at a later stage their rate falls below the normal(Heubel), and there is a decreased responsiveness to ex-ternal stimuli. Dif-ferent frogs varygreatly as regardsboth the ease withwhich they may behypnotized, and theduration of the hyp-notic state. In somecases if a frog is sim-ply placed on its backwithout being held,it may become hyp-notized after it hasrighted itself a fewtimes, and lie for along time in somephase of the pro-cess of turning of Ranaesculenta, accordingto Verworn, when laid on their backs, sometimes quicklydraw the hind legs close to the body, close their eyes, andlie with their muscles in a state of tonic contraction, — acondition which suggests the death feigning of certaininsects. Tonic contractions of different parts of the body may 1 Verworn, Die sogenannte Hypnose der Thiere, FIG. 7. — Rana temporaria in the so-calledhypnotic state. The upper figure showsthe position assumed when the back isrubbed with the finger. The same attitudeis maintained when the frog is placed onits back, as is shown in the lower figure.(Modified from Verworn.) II HABITS AND NATURAL HISTORY OF THE FROG 61 often be induced by rubbing the back and sides. If thefrogs are in a normal resting position, they frequently raisethemselves up on their legs and remain motionless and rigidfor some time. If when in this state they are laid on theirbacks, the legs still retain the same attitude as before. Frogs may be awakened from their state of hypnosis byany sudden stimulus, and their recovery is often duration of this state may be much prolonged if allsensory impressions are so far as possible removed. REFERENCES See especially the works of Abbott, Allen, Boulenger, Brehm, Dume-ril et Bibron, Diirigen, Fischer-Sigwart, Hay, Gadow, Leydig, Roselvon R
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