. The elementary nervous system. Nervous system; Nervous system -- Coelenterata. 92 THE ELEMENTARY NERVOUS SYSTEM. Nevertheless, when the middle of this piece is stimulated mechanically or by discharging on it a small amount of hydrochloric acid in sea- water, a withdrawal of the whole oral disc follows. This response ceases when all the organic connections of the piece with the rest of the ani- mal are severed by cutting through the attached mesen- teries, thus allowing the piece Fio. 22.—Metridium in whose column simplv to He ill plaC6 OH the wall an oblong incision, 4 cm. by 2 cm., a\\±:dTo
. The elementary nervous system. Nervous system; Nervous system -- Coelenterata. 92 THE ELEMENTARY NERVOUS SYSTEM. Nevertheless, when the middle of this piece is stimulated mechanically or by discharging on it a small amount of hydrochloric acid in sea- water, a withdrawal of the whole oral disc follows. This response ceases when all the organic connections of the piece with the rest of the ani- mal are severed by cutting through the attached mesen- teries, thus allowing the piece Fio. 22.—Metridium in whose column simplv to He ill plaC6 OH the wall an oblong incision, 4 cm. by 2 cm., a\\±:dTo1ne9:n?maaitoniybUytih!reC8een! sea-anemone. The cessation teries. stimulus applied at x. Of reSp0nse under these cir- cumstances shows that the transmission from the surface to the muscle must have been nervous and that it was not due either to the mechanical effects of the contraction of the piece itself on the deeper tissue, or to an accidental overflow of acid. Thus this experiment, like the two preceding ones, demonstrates a direct nervous con- nection between the ectodermic sensory apparatus of the col- umn wall and the longitudinal muscles of the mesenteries. If a sea-anemone is cut in two vertically in such a way that the resulting halves remain attached only by the lips (Fig. 23), not even the oesophagus or the oral disc remaining intact, and. 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 Parker, George Howard, 1864-1955. Philadelphia, London J. B. Lippincott Company
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