. American journal of physiology. light in relaxation or decrease oftonus, especially as this reaction of the heart on stimulation of thecardio-inhibitory nerves is very marked in the cephalopods. A seriesof experiments were carried out to test this hypothesis. The sus-pended ventricle was made to complete a circuit, the platinum hook 420 A. J. Carlson. which supported the ventricle and the silk ligature at the auriculo-ventricular junction serving as poles on the ventricle, the silk threadbeing moistened with the blood plasma. This circuit, as well as theelectrodes by which the commissures we
. American journal of physiology. light in relaxation or decrease oftonus, especially as this reaction of the heart on stimulation of thecardio-inhibitory nerves is very marked in the cephalopods. A seriesof experiments were carried out to test this hypothesis. The sus-pended ventricle was made to complete a circuit, the platinum hook 420 A. J. Carlson. which supported the ventricle and the silk ligature at the auriculo-ventricular junction serving as poles on the ventricle, the silk threadbeing moistened with the blood plasma. This circuit, as well as theelectrodes by which the commissures were stimulated, were connectedwith a commutator without cross bars, st) that the induced currentcould be sent directly through the suspended ventricle or throughthe nerves at will. When a strong interrupted current is sent directlythrough the ventricle, a strong tonus with a rapid series of diminutivebeats is produced, lasting for some time after the cessation of thestimulation, the longer, the stronger the stimulus. When the in-. 111111 i 1111111111111111111111 Figure 11. — Quiescent ventricle of Aplysia. d, direct stimulation of the ventricle withthe strong interrupted current, z/i, stimulation of the ventricular nerve, vc, stimula-tion of the pleuro-visceral commissures. Showing rhythm and further tonus contrac-tion on stimulation of the heart nerves. Time in seconds. terrupted current is very strong, no beats at all appear on the tetanusor tonus curve. If on the cessation of the direct stimulation of theventricle, the ventricle being in strong tonus or tetanus, the inter-rupted current of moderate strength i« applied to the commissures,no decrease in the tonus or relaxation of the ventricle is producedunder any conditions ; but when the stimulation of the nerves affectsthe ventricle at all, the effects are in the line of acceleration of thebeats or further increase in the tonus or tetanus contraction. Thisis fully illustrated by the tracings reproduced in Fig. ii. In Fig.
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