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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    a central nervous organ. There are, however, various other parts which have been taken for nerves, but some of these, certainly, do not belong to this system. In the Cystici, no nervous system has yet been found, and the researches made upon the Oestodes have ended equally unsatisfactory. A single observation upon a Tetrarkyncus would lead us to think that in these last the nervous system is situated at the cephalic extremity. In Tetrarhynchus attenuatus, there is a small flattened swelling between the sheaths of the four probosces, and from which pass off filaments to both of these organs..’11 The observations upon the nervous system of the Trcmatodes are more numerous and positive. Immediately behind the oral sucker, and upon the sides of the oesophagus, are two nervous swellings, connected by a transverse cord, which passes beneath this canal. Among the branches given off in all directions from these, there are two, large and long, extend- ing from each side of the body to its extremity, and which give off in their course many lateral branchlets.® In Pentastomum, the central portion of this system consists of a single large ganglion, sub-oesophageal, and due perhaps to the fusion of two lateral ganglia. From this, filaments pass off in every direction; two of these surround the oesophagus in a ring-like manner, while two others, analogues of the two main trunks of the Trematodes, pass to the very extremity of the body, giving off on their way, very fine filaments.3 1 Muller, not without reason, regards this organ as the nervous system of Tetrarhynchus (Arch. 1836, p. CVI.). New observations are needed to decide if, as Lereboullet (Institut. 1839, No. 812, p. 118) supposes, there can be included in this sys- tem the two longitudinal stripes, which, with Ligu- la simplicissima, extend along both sides of the ventral surface, and from which I, at least, have seen pass no filaments.* 2 Our very exact knowledge of the nervous sys- tem of Amphistomum subtriquetrum, and coni- cum, and of Distomum hepaticum, we owe to the researches of Bojahus (Isis 1821, p. 168, Taf. II. fig. 14, 15, 19), of Laurer (De Amphistomo co- nico, p. 12, fig. 21, 26), and of Mehlis (De Disto- mate hepatico, p. 22, tig. 13). By continuing the methods of these helmintholo- gists, this system will undoubtedly be found in other Trematodes. Diesing (Ann. d. Wiener Mus. I. Abth. 2, p. 246, Taf. XXLI. fig. 9) has found in Amphistomum. giganteum, and I have done the same in Distomum duplicatum (which is prop- erly only a larva of a species of this genus) the same disposition noticed in Amphistomum coni- cum. In Distomum holostomum, I have found also a similar structure, except that the two oesoph- ageal ganglia are widely separated, and united by a very long cord-like commissure. Laurer alone affirms to have seen enlargements upon the principal nervous trunks of the Trematodes. But their existence may be yet doubtful for no other anatomist has mentioned them, and in no case have I myself been able to see them. ^ 3 Miram (Nov. Act. Acad. XVII. pt. 2, p. 632. * Tab. XLVI. fig. 8) did not, apparently, notice in Pentastomum taenioides the nervous ring which surrounds the oesophagus ; although it had already been noticed by Cuvier (Regne Anim. III. 1830, p. 254), and by Nordmann, in a work in common with Mehlis (Microgr. Beitr. lift. 2, p. 141). The existence of this ring has been placed beyond a doubt by the figures of it as found in Pentasto- mum taenio'ides, and proboscideum, given by Owen (Trans, of the Zool. Soc. I. p. 325, PI. XI. fig. 13, or Cyclop. Anat. and Phys. II. p. 130, fig. *78), and Diesing (Ann. d. Wiener Mus. I. Abth. 1, p. 13, Taf. I. H.).f * [ § 104, note 1.] Blanchard (Ann. d. Sc. Nat. 1848, X. p. 338) appears to have distinctly made out a ribrvous system in Taenia. With Taenia serrata, there are directly behind the proboscis two small medullary nuclei united by a commissure *, from these pass off on each side a nerve which is distributed to the lateral parts of the head, and connects with a ganglion situated at the base of each sucker, which sends filaments to the muscles of this last. Posteriorly there are given off filaments which run parallel to the intestinal tubes. This, however, has not been confirmed by other observers, and Agassiz has made a statement in a private letter to me which is worthy of notice. 10 He says : u I believe the nervous system described by Blanchard to be bands of muscular fibres which cross each other between the fossae of the probos- cis •. at least, this is so in the new species of Taenia from Amia calva which was observed alive for sev- eral hours ; and I could discover no nervous threads, but only muscular fibres, which had ex- actly the arrangement of Blanchard's nervous sys- tem.” See, however, Valenciennes' report to the Acad, des Sc. in the Comp. Rend. 1847, XXIV. p. 1034, also Blanchard's response to Dujardiny Ibid. 1849, XXIX. p. 60.—Ed. t [ § 104, note 3.] Blanchard has found with Linguatula another ganglion above the cesopha-