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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    The central nervous system of the Acanthocephali is very distinct. It is always concealed at the bottom of the sheath of the proboscis, which this last, being never in a state of complete retraction, does not fill. It consists of a dense mass of ganglionic, cellular globules blended together, and here and there may be seen through the cell-membranes their nuclei and corpus- cles. This comparatively large mass sends off nerves in every direction, but the tenuity of these prevents their being traced, especially after they have entered the muscular walls of the proboscideal sheath.(4) With the Glordiacei,® and Nematodes, a nervous system has been found with certainty only in Strongylus gigas. Here a cord arises from a swell- ing in the head, traverses the whole ventral line, and terminates at the swelling. It sends off in its course nervous system of the Sipunculidae.® 4 I have thus found the nervous system of the Acanthocephali in Echinorhyncus gigas, angus- tatus, haeruca, and proteus. It can be easily ob- served by carefully pressing or tearing the probos- cideal sheath. In thus tearing, you sometimes completely expose the ganglionic mass with the roots of the nerves. In no species that I have dis- sected have I been able to find the ganglionic ring mentioned by Henle (Froriep's neue Not. No. 285, p. 330, and Muller's Arch. 1840, p. 318)‘as found about the genital orifice of Eckinorhyncus nodulosus. Dujardin also (Hist. Nat. d. Helm. p. 495, 491, PI. VII. fig. D. 4), has not observed it, but he dis- tinctly perceived the central mass at the base of the proboscis, and has figured and named it as un corps glanduleux oil ganglionaire. 5 As yet no nervous system has been found in the Gordiacei. Bert ho Id (Cber den Bau des Gor- dius aquaticus, 1842, p. 12) has been inclined to regard as nerves two delicate filaments which traverse the cavity of the body of Gordius ; but, a3 these give off no lateral branches, this opinion cannot be admitted.* 6 Many Helminthologists have erroneously taken for nerves the delicate projecting fines which, situ- gus, which he regards as a brain ; these observa- tions have since been confirmed by Van Beneden (Ann. d. Sc. Nat. XI. 1849, p. 319), who, however, regards this mass as belonging to the sympathetic system. But, however viewed, an oesophageal col- lar has been distinctly made out, thus confirming the views of Cuvier. In regard to the splanchnic system of nerves with these animals, Van Beneden (loc. cit.) de- scribes it as consisting of two ganglia lying on the oesophagus back of the oesophageal collar, and from which pass off two filaments, which run along the oesophagus, and enter the collar laterally. He thinks the two ganglia are united by a transverse length of the body upon the median posterior end of the body in another lateral filaments, thus resembling the ated directly subcutaneous and often blended with the skin, traverse the whole length of the body of many Nematodes, and have been called the ventral and dorsal lines. Their lateral branches, as already observed, are only transverse muscular bands. Quite different from these is the longitudinal cord, which Otto (Magaz. d. Gesellch. naturf. Freunde zu Berlin, 7^ Jahrg. 1816, p. 225, Taf. V.) has described and figured as belonging to the nervous system •, a view which I am disposed to adopt, in spite of Nitzsch (Erscli and Gruber's Encyclop. VI. 1821, p. 45) and other Helminthologists. In a large female Strongylus gigas, now under my eyes, there is a simple longitudinal cord beneath the muscular envelope, and therefore in direct con- nection with the skin, and which extends along the ventral surface. In its course it sends off numberless lateral branches, which in their inti- mate structure are quite different from the trans- verse muscular bands. But neither here nor upon the nerves of other worms have I ever seen the enlargements spoken of by Otto. Grant's figure of a double nervous filament traversing the body of Ascaris is probably imaginary j see Outlines of Comp. Anat. p. 186, fig. 82, A. commissure. Further behind is another and larger ganglion on each side, and from which pass off filaments to the digestive cavity. See also my note under § 99. — Ed. * [ § 104, note 5.] This view of Berthold is sup- ported also by Blanchard (Ann. d. Sc. Nat. 1849, XII. p. 6), who affirms that he has observed on both sides of the body a double longitudinal cord, which is usually very distinct. This, examined microscopically, appeared to be composed like the nerves of the other Ilelminthes. Blanchard, how- ever, did not succeed in tracing these cords to any cephalic centres. Nothing of special value, there- fore, is known on this subject. — Ed.