. Comparative physiology of the brain and comparative psychology. Brain; Psychology, Comparative. i8 COMPARATIVE PHYSIOLOGY OF THE BRAIN Our first question is : Is the spontaneous locomo- tion of the Medusae, or the rhythmical contraction of their swimming-bell, a function of the ganglion-cells ? Romanes found - that if the margin of the bell of a Hydro- medusa (6, Fig. 3) be cut off, the rhythmical contraction of the centre of the bell (a, Fig. 3) ceases, while FIG. 2. DIAGRAM OF THE BELL OF AURELIA t\\Q margin b which AURITA, WITH EIGHT SENSE ORGANS. (After ciaus.) contains the nerve- ring,
. Comparative physiology of the brain and comparative psychology. Brain; Psychology, Comparative. i8 COMPARATIVE PHYSIOLOGY OF THE BRAIN Our first question is : Is the spontaneous locomo- tion of the Medusae, or the rhythmical contraction of their swimming-bell, a function of the ganglion-cells ? Romanes found - that if the margin of the bell of a Hydro- medusa (6, Fig. 3) be cut off, the rhythmical contraction of the centre of the bell (a, Fig. 3) ceases, while FIG. 2. DIAGRAM OF THE BELL OF AURELIA t\\Q margin b which AURITA, WITH EIGHT SENSE ORGANS. (After ciaus.) contains the nerve- ring, continues to ex- ecute rhythmical contractions (2). The wound does not even cause a decrease in the number or in the strength of the marginal contractions. The exper- iment has been repeated by other authors with the same result. Any sort of wound can be made in the umbrella without disturbing the rhythmical con- tractions so long as the nerve-ring remains intact. Thus Romanes concluded that these rhythmical con- tractions of Hydromedusse originate in the nerve- ring or its ganglia. I have found recently that this whole problem is not so much a morphological problem as a problem of physical chemistry. The osmotic pressure of the sea-water is about equal to that of a -| n NaCl solution. I found that if the centre of a swimming-bell be put into a -| n NaCl or |- n NaBr solution it goes on beating rhythmically. But if a. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Loeb, Jacques, 1859-1924. New York, G. P. Putman's Sons; [etc. , etc. ]
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