An American text-book of physiology . per cent, in thefrequency of the heart-beat (see Fig. 119). The quicker the heart is beatingbefore thn stimulation, the less marked is the acceleration. The absolute maxi- Fig. 119.—Curve of blood-pressure in the cat, recorded by a mercury manometer, showing theincrease in frequency of heart-beat from excitation of the augmentor nerves. The curve reads fromright to left. The augmentor nerves were excited during thirty seconds, between the two stars. Thenumber of beats per ten seconds rose from 24 to 33 (Boehm, 1875, p. 258). mum of frequency is, however, i
An American text-book of physiology . per cent, in thefrequency of the heart-beat (see Fig. 119). The quicker the heart is beatingbefore thn stimulation, the less marked is the acceleration. The absolute maxi- Fig. 119.—Curve of blood-pressure in the cat, recorded by a mercury manometer, showing theincrease in frequency of heart-beat from excitation of the augmentor nerves. The curve reads fromright to left. The augmentor nerves were excited during thirty seconds, between the two stars. Thenumber of beats per ten seconds rose from 24 to 33 (Boehm, 1875, p. 258). mum of frequency is, however, independent of the frequency before stimulation.^The maximum of acceleration is largely independent of the duration of stimula-tion. The duration of stimulation and the duration of acceleration are notrelated, a long stimulation causing no greater acceleration than a short one.^ The/o>-ce of the ventricular beat is increased.* The ventricle is filled morecompletely by the auricles, the volume of the ventricle being increased. The. ^rr / yV /i-c r/ Fig. 120.—Increase in the force of the ventricular contraction (curve of pressure in right ventricle) fromstimulation of angmentor fibres. There is little or no change in frequency (Franck, 1890, p. 819). output of the heart is There is no definite relation between the in-crease of contraction volume or force of contraction and the increase in fre-quency (see Fig. 120). Either may appear without the other, though this is Gaskell, 1884, p. 48. Boehm, 1875, p. 277. ^ Baxt, 1877, p. 523. * Heidenhain, 1882, p. 396; Ga-skell, 1884, p. 47; 1886, p. 42; Mills, 1886, p. 554; Franck,1890, p. 814; Roy and Adami, 1892, p. 242; Baylies and Starling, 1892, p. Roy and Adami, 1892, p. 240. CIRCULATION. 461 rare.* The simultaneous stimulation of the nervesof Ijoth sides does notgive a greater maximum frequcncv than the stimulation of one nerve alone.^ The strength and the volume of the auricular contractions are also in-creased.
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