Archive image from page 779 of The cyclopædia of anatomy and. The cyclopædia of anatomy and physiology cyclopdiaofana01todd Year: 1836 M 7 Nervous system of the Attacvs Marinns, or Sphinx Ligustri. in consequence of their gliding or encroaching, as it were, upon the median line. The Lobster ( Astacusmarinus)(jig. 393) pre- sents us with another step in the system of cen- tralisation. Here, in fact, the longitudinal cords of communication are entirely consolidated along the median line through the whole of the abdomen, although they are still to be found double in the thorax. Moreover, the fir
Archive image from page 779 of The cyclopædia of anatomy and. The cyclopædia of anatomy and physiology cyclopdiaofana01todd Year: 1836 M 7 Nervous system of the Attacvs Marinns, or Sphinx Ligustri. in consequence of their gliding or encroaching, as it were, upon the median line. The Lobster ( Astacusmarinus)(jig. 393) pre- sents us with another step in the system of cen- tralisation. Here, in fact, the longitudinal cords of communication are entirely consolidated along the median line through the whole of the abdomen, although they are still to be found double in the thorax. Moreover, the first thoracic ganglion (£•>), and the last of the abdominal series of ganglions (a6), are conspicuously formed by the reunion of several distinct ner- vous centres, in the way we have already indi- cated as happening, although in a minor degree and less perfectly, in the Amphipoda and the Isopoda. Before we pass, however, to the con- sideration of more complicated systems, we shall pause a moment to describe somewhat at length the one which we have but just mentioned, the more as it is among the number of those which have been most attentively studied. The cephalic ganglion (gfig. 393), situated above the base of the internal antennae, is of con- siderable size, and appears to be simple ; it gives origin to five pairs of nerves and to two cords, which connect it with the rest of the ganglionic nervous system. The first of these pairs (o)arises from its anterior edge: this is the optic pair, which, after having penetrated the peduncles of the eyes, increase in size, and traverse a mem- branous diaphragm, which may be likened to the sclerotic coat. The second pair of nerves correspond to the ocular motors ; they run parallel to the pre- ceding pair, and are distributed to the muscles of the eyeball. The third pair proceed to the internal anten- nae (6); but before they enter these appendages they send off a branch to the muscles which move them. A like ramification is sent
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