American journal of physiology . ation of what character and what duration artificially produced Action of the Vagus Nerve on the Heart. 493 arrest ought to be. The best arrest I hold to be that obtained with•currents of minimal intensity and duration. The vagi, or their terminations in the heart, are very soon rest of at least two minutes between successive stimulations isnecessary. The heart is to be kept moist. Very useful for this is a physiologi-cal gelatine solution (5 grams of gelatine dissolved with the aid in 300 grams of normal saline solution). II. The Effect of V
American journal of physiology . ation of what character and what duration artificially produced Action of the Vagus Nerve on the Heart. 493 arrest ought to be. The best arrest I hold to be that obtained with•currents of minimal intensity and duration. The vagi, or their terminations in the heart, are very soon rest of at least two minutes between successive stimulations isnecessary. The heart is to be kept moist. Very useful for this is a physiologi-cal gelatine solution (5 grams of gelatine dissolved with the aid in 300 grams of normal saline solution). II. The Effect of Vagus Excitation on the Intervalbetween the contraction of the several parts of theHeart. I. The auriculo-veutricular interval. — The interval between the con-tractions of the auricle and ventricle is usually prolonged when thevagi are stimulated. Sometimes, however, especially with very weakcurrents, the duration of the interval is not affected, although theforce of the auricular systole is diminished. This is in fact a most. Figure 2. Four-fifths the original size. The uppermost curve records the movementsof the ventricle (R. temporaria); the second curve, the movements of the elevation in the third curve marks a reflex stimulation from the stomach (tetaniza-tion). The fourth curve was written by a tuning fork swinging lo times a second. common effect of weak vagus stimulation. In Fig. 2 the intervalsare 43, 43, 42, 43, 61, 63, 69, 73, 66, 52, and 46 hundredths second,reading from left to right. As a rule the increase reaches its maxi-mum rapidly and then slowly decreases. A second maximal valueis often observed as an after effect. Figure 3 is an example of the effect of a stronger vagus height of contraction is diminished in the first auricular systoleafter the stimulation, but no measurable increase in the auriculo-ven-tricular interval is observed until the next cardiac cycle. Then theinterval, which had been 39, 40, 40, 40, increases to 63 hu
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