. The brain as an organ of mind. Brain; Thought and thinking; Brain. 88 THE NERVOUS SYSTEM OF VERMES. as to form three or four nerve-trunks on each side, which enter a comparatively large compound ganglionic mass (a, a) lying on the lateral aspects of the sheath of the prohoscis. Each of these masses is pyriform in shape, and composed of a sensory and a motor ganglion fused into one. It is connected with its fellow by means of two commissures, one of which passes over, and the other beneath, the proboscis. It is difficult to trace the ultimate distribution of the nerve-fibres in these crea- tu
. The brain as an organ of mind. Brain; Thought and thinking; Brain. 88 THE NERVOUS SYSTEM OF VERMES. as to form three or four nerve-trunks on each side, which enter a comparatively large compound ganglionic mass (a, a) lying on the lateral aspects of the sheath of the prohoscis. Each of these masses is pyriform in shape, and composed of a sensory and a motor ganglion fused into one. It is connected with its fellow by means of two commissures, one of which passes over, and the other beneath, the proboscis. It is difficult to trace the ultimate distribution of the nerve-fibres in these crea- tures ; so that, although fibres can be followed nearly up to the pigment-spots, none have been detected in immediate continuity there- with. The inferior com- missure (c) between the two. Fig. 30.—Head and Brain of a Nemertean. {Tetrastemma vielanoce'phala.) a, o, Com- pound lateral ganglia; b, narrow upper ganglionic maSSCS is sllOrtcr commissure between which and the much thicker inferior commissure, c, the oesopha- giis passes ; c?, d, the great lateral nerve cords; e, e, pigment spots, or rudimentary ocelli. (After Mcintosh.) and much thicker than the upper. The two great late- ral nerve-trunks {d, d) start from the ganglia, and, pro- ceeding along the sides of the body, give off numerous branches to the longitudinal and circular muscles betv/een which they are situated. Tactile and possibly gustatory impressions, together with impressions produced by light or darkness, doubtless come from the anterior extremity of the organism to the anterior part of the pyriform ganglia on either side ; and are thence reflected from the posterior parts of these bodies. 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 Bastian, H. Charlton. N. Y. , Appleton
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectbrain, booksubjecttho
