. An elementary course of practical zoology. Zoology. NERVOUS SYSTEM 333 the former of a well-developed nervous system (p. 311) consisting of an arrangement of peculiarly modified cells, was seen to be due. It is to which automatic action such an active and otherwise as the earthworm a nervous sys- ^.â prcst y'y- natural to expect in highly-organised animal tern of a considerably higher degree of com- plexity than that of a medusa. The central ner- vous system consists of two parts, the braiji and the ventral nerve- cord. The brain (Fig. 79 br, and Fig. 81, cer. gang) consists of a pair of whi
. An elementary course of practical zoology. Zoology. NERVOUS SYSTEM 333 the former of a well-developed nervous system (p. 311) consisting of an arrangement of peculiarly modified cells, was seen to be due. It is to which automatic action such an active and otherwise as the earthworm a nervous sys- ^.â prcst y'y- natural to expect in highly-organised animal tern of a considerably higher degree of com- plexity than that of a medusa. The central ner- vous system consists of two parts, the braiji and the ventral nerve- cord. The brain (Fig. 79 br, and Fig. 81, cer. gang) consists of a pair of white pear- shaped swellings or ganglia situated on the dorsal side of the buccal sac where it is continued into the pharynx. The ventral nerve - cord (n. c and ne. cd) is a longitudinal band extending along the whole middle ventral line of the body, internally to the longitudinal muscular layer, from the third to the anal segment, and slightly swollen in each segment. The brain is connected with the anterior end of the ventral nerve-cord by a pair of nervous bands, the (esophageal connectives (com) which pass respectively right and left of the buccal sac, and thus form a Fig. Si.âAnterior portion of nervous s^'stem of Liifjibricrcs. :, cerebral ganglia or brain ; com. oeso- phageal connectives ; nc. co. ventral nerve-cord ; prost. prostomium. (From Parker and Has- well's Zoology^ after Leuckart.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Parker, T. Jeffery (Thomas Jeffery), 1850-1897; Parker, William Newton, joint author. London, Macmillan and Co. , Limited; New York, The Macmillan Company
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