. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 110 IPING CHAO solution to a sucrose solution containing KC1 in the concentration nor- mally present in Ringer's solution ° (Fig. 4). The Calcium-paradox When a ganglion is immersed in a Ca-free Ringer's solution for sev- eral minutes the rate of the heart-beat is accelerated considerably. If then the Ca-free Ringer's solution is replaced by a normal Ringer's solu- tion, the rate falls progressively to normal (rapidly at first and more gradually later), while the amplitude undergoes a somewhat rapid de- crease to a minimum h
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 110 IPING CHAO solution to a sucrose solution containing KC1 in the concentration nor- mally present in Ringer's solution ° (Fig. 4). The Calcium-paradox When a ganglion is immersed in a Ca-free Ringer's solution for sev- eral minutes the rate of the heart-beat is accelerated considerably. If then the Ca-free Ringer's solution is replaced by a normal Ringer's solu- tion, the rate falls progressively to normal (rapidly at first and more gradually later), while the amplitude undergoes a somewhat rapid de- crease to a minimum height followed by a period of gradual rise to nor- mal (Fig. 5). This primary and temporary decrease in amplitude on change from a Ca-free to a normal Ringer's solution resembles that observed in the K-paradox, though it is less pronounced, and is known. FIG. 5. Experiment No. 26. (a) Ca-paradox obtained on change from a Ca- free to a normal Ringer's solution after the ganglion lias been immersed in the former for twenty minutes, (b) Eighteen minutes later in the normal Ringer's solution. as the Ca-paradox. Like the K-paradox, it is more readily obtained on a second or a third repetition than on the first immersion of a fresh ganglion in the Ca-free Ringer's solution; and the primary decrease in amplitude is greater after a longer period of immersion in the Ca-free Ringer's solution. The change illustrated in Fig. 5, for instance, was obtained after an immersion of a fresh ganglion in the Ca-free Ringer's solution for twenty minutes; a second immersion for ten minutes gave a very small primary decrease in amplitude indeed. The Ca-paradox differs from the K-paradox essentially in two re- spects. In the first place, the primary temporary inhibition affects the amplitude only; during the process of recovery, the rate returns pro- 6 The K-paradox can be more readily demonstrated on change from a K-free Ringer's solution to a sucrose solution containing Please note that these
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