File:The brain as an organ of mind (1896) (14760929976).jpg

Identifier: brainasorganofmi00bast (find matches)
Title: The brain as an organ of mind
Year: 1896 (1890s)
Authors: Bastian, H. Charlton
Subjects: Brain Nervous System Physiology Brain Nervous system Psychology, Comparative
Publisher: New York : D. Appleton and Company
Contributing Library: University of Connecticut Libraries
Digitizing Sponsor: University of Connecticut Libraries

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ks of pig-ment are met with (fig. 30, e, e), which are conjectured toserve the purpose of rudimentary ocelli; and whilst theanimal is moving from place to place this anterior part ofits body doubtless acts also as its principal tactile surface.Nerve-fibres proceed from these regions, and converge so 88 THE NERVOUS SYSTEM OF VERMES. as to form three or four nerve-trunks on each side, whichenter a comparatively large compound ganglionic mass(a, a) lying on the lateral aspects of the sheath of theproboscis. Each of these masses is pyriform in shape, and composed of a sensory anda motor ganglion fused intoone. It is connected withits fellow by means of twocommissures, one of whichpasses over, and the otherbeneath, the proboscis. It is difficult to trace theultimate distribution of thenerve-fibres in these crea-tures ; so that, althoughfibres can be followed nearlyup to the pigment-spots,none have been detected inimmediate continuity there-with. The inferior com-missure (c) between the two
Text Appearing After Image:
Fig. 30.—Head and Brain of a Nemertean.(Tetrastemma melanocep/iala.) a, o. Com-pound lateral ganglia ; h, narrow upper ganglionic maSSCS is sllOrtcrcommissure between which and the muchthicker inferior commi-ssure, c, the cesopha- and much thicker than the gus passes ; d, d, the great lateral nerve upper. The tWO great latC-cords ; e, e, pigment spots, or rudimentary 177 ocelli. (After Mcintosh.) ral nervc-trunks (a, a) start from the ganglia, and, pro-ceeding along the sides of the body, give off numerousbranches to the longitudinal and circular muscles betweenwhich they are situn,ted. Tactile and possibly gustatory impressions, togetherwith impressions produced by light or darkness, doubtlesscome from the anterior extremity of the organism to theanterior part of the pyriform ganglia on either side ; andare thence reflected from the posterior parts of these bodies Chap, v.) THK NERVOUS SYSTEM OF VERMES. 89 along related channels in the great efferent handles, thefibres of which pro

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