Comparative anatomy / by C.Th. v. Siebold and H. Stannius ; translated from the German, and edited with notes and additions recording the recent progress of the science by Waldo I. Burnett.

  • Karl Theodor Ernst von Siebold
Date:
1854
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Licence: Public Domain Mark

Credit: Comparative anatomy / by C.Th. v. Siebold and H. Stannius ; translated from the German, and edited with notes and additions recording the recent progress of the science by Waldo I. Burnett. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    CHAPTER III. NERVOUS SYSTEM. § 79. The central portion of the nervous system consists of a ring which is usually pentagonal, and surrounds the commencement of the oesophagus. The main nervous branches are given off from this, and pass to the other end of the body along the median line of the rays, or their corresponding parts. The form of this ring is mainly due to that of the mouth; and therefore, with the reniform mouth of Spatangus, it is unequally pentago- nal.05 Ganglia have not yet been found in it. But in Echinus and Holo- thuria, the nerves passing from it have between their fibres, violet, green, or red pigment granules.® §80. The principal nervous trunks have a longitudinal furrow, as if composed of double cords, and give off from each side, during their course, branches which go to the ambulacra.® With the Crinoidea, a nervous cord passes beneath the furrow formed by the perisoma on the ventral surface of the arms; this has a slight swelling opposite each pinnula, to which it sends off a branch.® With the Asteroidae, the nervous trunks which pass off from the oesophageal ring are lodged in the ventral furrows of the rays.® But in the Ophiuridae, they pass in a canal, concealed by the ventral plates of the arms. The five nerves, analogous to those of the Echinoidea, pass along the internal surface of the ambulacral plates, between the vesicles, even to the centre of the dorsal region. In Echinus, there are, moreover, special nerves directly from the oesophageal ring, for the organs of mastication and digestive canal.® In Holothuria, this ring is situated directly on the anterior border of the osseous circle, and sends off' five nerves which pass along the median line of the longitudinal muscles, even to the end of the body ;(5) it sends off also special nerves to the oral tentacles.® 1 Krohn (Muller's Arch. 1841, p. 8, Taf. I. fig. 3,4). 2 Krohn, loc. cit. 1 Krohn, ibid. p. 4, 10. 2 Muller (Abhandl. d. Berl. Akad. loc. cit. p. 233, Taf. IV. fig. 11, i. ; Taf. V. fig. 16). 3 The nervous system of the Asteroidae was first clearly shown by Tiedemann (loc. cit. p. 62, Taf. IX. and MeckeVs Deutsch. Archiv. I. 1815, p. 69, Taf. III. fig. 1). This anatomist, like Krohn (loc. cit. p. 4), did not perceive the ganglia of the oesophageal ring, observed by Wagner (Vergleich. Anat. 1834, p. 372). The ganglia and nerves that Spix (Ann. du Mus. d’Hist. Nat. XIII. 1809, p. 439, PI. XXXII. fig. 3, 6) and Konrad (De Asteriarum fabrica dissert. 1814, p. 13, fig. 3, o.) affirm to have seen on the internal (dorsal) surface, opposite the ventral * (§ 80, note 6.] Muller has furnished some valuable contributions on the nervous system of the furrows of the articulations of the rays, in Aster- acanthion rubens, and glacialis, are probably only tendinous fibres. 4 Krohn, who has studied the nervous system of Echinus and Spatangus, has traced the fila- ments given off from the main trunks, across the ambulacral pores, to the suckers of the ambulacra. See also Valentin's figures of tliis system, in EchinHs (Monogr. loc. cit. p. 98, PI. VIII. IX.). 5 The oesophageal ring of Holothuria, observed by Krohn (.Muller's Arch. 1841, p. 9, Taf. I. fig. 5), sends off its principal nerves across the fissures of the dentations of the five great pieces of the osseous rings. Then* lateral filaments, going to the ambulacral vesicles, are so fine that Krohn could scarcely find them. 0 Grant, loc. cit. p. 184.* Ilolothurioidea; see Arch. 1850, p. 226. lie makes this statement, which is worthy of remem-