PARADOX PHENOMENA IN THE CARDIAC GANGLION OF LIMULUS POLYPHEMUS

¹ From the Marine Biological Laboratory, Woods Hole, and the Department of Physiology, University of Chicago

Potassium-paradox, calcium-paradox, and thermo-paradox have been observed in the ganglion of the Limulus heart.

The Ca-paradox is obtained on change from a Ca-free to a normal Ringer's solution, and the thermo-paradox is obtained on change from a warm to a cold Ringer's solution.

The K-paradox is obtained in a similar way on change from a K-free to a normal Ringer's solution, and its production depends upon the following factors:

1. The K-paradox is more readily obtained on the second or third repetition than on the first immersion of a fresh ganglion in the K-free Ringer's solution.

2. The paradoxical effect becomes more pronounced with increasing duration of the preliminary immersion in the K-free Ringer's solution.

3. The factor determining the K-paradox is the sudden change in the K-content of the medium surrounding the ganglion, and this change must be in the direction of increasing the K-content in the second solution.

4. The presence of a minimum amount of NaCl in the K-free Ringer's solution (about 30 per cent of the normal concentration) is necessary for the production of the K-paradox. The presence of CaCl₂ in the K-free, or the K-containing, solution is of only secondary importance perhaps by virtue of its antagonistic action.

In general the paradoxes found in the ganglion of the Limulus heart are essentially identical with those described in the vertebrate heart.