The brain as an organ of mind . locomotion ; the threeposterior nerves supply the re-maining legs, which answer tothe thoracic legs of hexapodInsects. (Owen.) Since the sub - oesophagealganglia are in part analogous,as already stated, with the me-dulla oblongata of vertebrateanimals, their fusion with thethoracic ganglia in Arachnida,as well as in Myriapoda, tends, Fig. 38.—Nervous System of a . /> great scorpion-like Spider {Thehj- m a mCaSUrC, tO COUlirm thO ). (Gegonbauer, after yj^^^y 1^q\([ ]jy c^^^j^q aUatomistS,Blaiiclian).) s, Cerebral ganglia ; /, . , greatventral
The brain as an organ of mind . locomotion ; the threeposterior nerves supply the re-maining legs, which answer tothe thoracic legs of hexapodInsects. (Owen.) Since the sub - oesophagealganglia are in part analogous,as already stated, with the me-dulla oblongata of vertebrateanimals, their fusion with thethoracic ganglia in Arachnida,as well as in Myriapoda, tends, Fig. 38.—Nervous System of a . /> great scorpion-like Spider {Thehj- m a mCaSUrC, tO COUlirm thO ). (Gegonbauer, after yj^^^y 1^q\([ ]jy c^^^j^q aUatomistS,Blaiiclian).) s, Cerebral ganglia ; /, . , greatventral ganglion, comnumicat- that it is better tO regard tllC ing with five large nerves on eaeh ^nicdulla aS a proloUgatioU of Mflc; 0, eyes; p, palpi; 2 2^, lect; ?•• c, tail-like prolong itiun. tlic spiual cord, than as an in- tegral part of the brain. Theartificial line, that is, which for convenience is drawnbetween the brain and the cord in Vertebrates, should beplaced at the upper rather than the lower or posterior. Chap. VI.] NERVOUS SYSTEM OF ARTHROPODS. 101 boundary of the medulla, so tliat the latter part maybe regarded as the more highly developed portion of thespinal cord by which fusion with the hrain is effected. The visceral nerves are well developed in the higherArachnida. They consist of one or two filaments, onwhich a ganglion may exist, in connection with the posteriorpart of the brain, and thence proceeding to the stomachand other internal organs. There are, moreover, two orthree branches given off from the great ventral ganglionwhich, after passing through smaller ganglia, distributenumerous filaments to the intestines, the respiratoryand genital organs, as well as other viscera. The formerset may be in the main afferent, and the latter perhapsprincipally efferent visceral nerves. Organs of vision are much more elaborate in Crustacea,Spiders and Insects, than among Worms or , whilst organs of touch and taste are further perfected,two sensory e
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