Vestiges of the natural history of creation / [Anon].

  • Robert Chambers
Date:
1844
Catalogue details

Licence: Public Domain Mark

Credit: Vestiges of the natural history of creation / [Anon]. Source: Wellcome Collection.

    343/408 page 335
    in different classes and species, and also in different individuals, the volume or mass bearing a general relation to the amount of power. Passing over the humblest orders, where nervous apparatus is so obscure as hardly to be traceable, we see it in the nematoneura of Owen* in filaments and nuclei, the mere rudiments of the system. In the articulata, it is advanced to a double nervous cord, with ganglia or little masses of nervous matter at frequent intervals, and filaments branching out towards each side ; the ganglia near the head being apparently those which send out nerves to the organs of the senses; and this arrangement is only less symmetrical in the mollusca. Ascending to the vertebrata, we find a spinal cord, with a brain at the upper extremity, and numerous branching lines of nervous tissue,f an organization strikingly superior; yet here, as in the general structure of animals, the great principle of unity is observed. The brain of the vertebrata is merely an expansion of the anterior pair of the ganglia of the articulata, * Including rotifera, entozoa, echinodermata, &c. { The ray, which is considered the lowest in the scale of fishes, or next to the crustaceans, gives the first faint representation of a brain in certain scanty and medullary masses, which appear as merely composed of enlarged origins of the nerves.
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