On the anatomy and physiology of the nematoids, parasitic and free : with observations on their zoological position and affinities to the echinoderms / by H. Charlton Bastian.

  • Bastian, H. Charlton.
Date:
[1866]
Catalogue details

Licence: Public Domain Mark

Credit: On the anatomy and physiology of the nematoids, parasitic and free : with observations on their zoological position and affinities to the echinoderms / by H. Charlton Bastian. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    piincipal roots, though in what precise manner could not he detected, owing to these parts being obscured by the dense fibrous meshwork which extends for some distance in front of the ring, as well as over much of the space between this and the head. The fibres composing this network are in part, rmdoubtedly, connecting nerve-fibres, though the greater portion of the tissue seems to be composed of mere protecting fibres, pro- bably derived from the muscles. Near the origin of these ventral nervi suhmediani, on either side, between them and the lateral tracts, are two small but distinct bipolar gan- glion-cells (Jc, k), one fibre of which seems to come from the oesophageal ring, whilst the other connects the cell with one of the nerves in question. The dorsal mrvi submediani (i, i) seemed to me principally derived from the ganglion-cells in the lateral tract poste- rior to the oesophageal ring, and appeared to cmwe gently upwards to supply the upper cephalic lobe. This lobe seemed also to derive fibres from two large nucleated ganglion- cells*, one of which is situated just external to each lateral tract (Ji, h), and also a small bundle of fibres from the nervi laterales. Although nerve-fibres have been detected only in the anterior part of the body of A. lumbricoides and other Nematoids, I have not the slightest doubt that peripheral branches do exist throughout the body generally; and from what I have seen of the course of one large fibre proceeding backwards from one of the lateral ganglion-cells, I suspect that they generally pass beneath the muscles to gain the deep cellular layer of the integument, in which they are principally distributed, and &om which they can so easily give off filaments to the muscles or to tactile papillae. I distinctly saw a fibre (marked e) lea\ing the substance of the lateral cord and passing beneath the muscular bundle lying outside it. Dr. Schxeidee seems inclined to think that some large nerve-fibres may pass posteriorly in the substance of the dorsal and ventral median lines, though he has never absolutely traced nerve-fibres passing from the central ring into these bodies. He rests his opinion upon the fact that in fine transverse sections which he has made of the median lines, he has found them perforated length- wise by caHties having an elliptical or oval cross section; which tubes or cavities, he states, are invariably filled with a transparent, homogeneous substance of a reddish or yellowish tint. He says that from six to eight such bodies can be detected in the ventral median hne of A. megaloce^phala, but only from four to six in the dorsal. These are considered to be transverse sections of nen’e-fibres; but the fact that they have a distinctly larger diameter than the piincipal nerve-fibres issuing from the ganglion-cells seems to me strongly opposed to this view. I have myself been unable to recognize such structures in the median lines, so must refer for further details concerning them to Dr. Schxeidee’s important memoir. The nervous system of Oxyuris curvula has also been carefully examined by Schxeidee, and in this animal he has found the oesophageal band most distinct, as well as the ante- rior fibres, though very few ganglion-cells could be detected. He has with difficulty, moreover, detected the most important parts of this nervous system in Strongylus * These large cells have rather a remarkable appearance from their isolated position, but stiU the aspect of their nucleus and cell-contents corresponds most closely with that of other ganglion-cells.