The Origin and Development of the Nervous System

Cephalization, nervous, definition of, 142. See also Centralization Conductor: as part of reflex arc, 233; in primitive gradient, 234. See also Excitation ; Transmission Correlation, chemical : significance of, 10, 12, 13; nature of, 13; in relation to organismic pattern, 14; in relation to external fac- tors, 14; in relation to differen- tiation, 93; in relation to origin of nervous system, 107 Correlation, physiological: organ- ismic and protoplasmic, n; three groups of, 12

Correlation, transportative, 10, 12, 13. See also Correlation, chemi- cal Cortex, cerebral: pyramidal cells of, 162, 166, 171; origin of, in relation to upward nerve paths, 261; physiological characteris- tics of, 263; electrical conditions as factor in development of, 263 Dedifferentiation: in consequence of physiological isolation, 103, limitation of, in higher forms, 105; in relation to tumors, 105 Dendrite, chaps, x, xi; in relation to functional irreversibility of reflex arc, 228

Differentiation: of organismic magnitude, 5; as a basis for chemical correlation, 14; in re- lation to susceptibility, 34; of nucleus, 61 ; in relation to physi- ological gradients, 90; in rela- tion to rate of intake and oxida- tion, 92; in animal egg, 94; in relation to symmetry, 96; of nervous structure in relation to physiological gradients, 108, 113, 115, 246; course of, along axes, 119, of neuron, chaps, x, xi; of receptor, conductor and effec- tor, 238

Dominance, physiological: in rela- tion to physiological gradients, 97,100; independent of nervous system, 99; in plants, 99; in Planar ia, 100; persistence of, independent of gradient, 102; range and limit of, 102, 104; as physiological independence, 118; in ctenophore plate row, 212; in vertebrate heart, 221; in rela- tions of neurons, 230; in anne- lids, 249; change in character of, in higher vertebrates, 259; in cerebral cortex, 266. See also Gradients, physiological

Equisetum, determination of polar- ity by light in spores of, 51 Galvanotaxis, as factor in develop- ment of neuron pattern, 1 73 Gradients, excitation, 235. See also Arc, reflex; Excitation, Gradients, physiological; Trans- mission Gradients, physiological : as prim- ary factor in axiate pattern, 24; as primarily superficial, 26, 32, 86; modifications of, during development, 26; evidence for existence of, 27; in relation to structure and development, 27; in relation to susceptibility, 32; reversal of, 33, 243; in relation to rate of penetration, 40; in relation to reduction of KMnO4, 42; in relation to indophenol reaction, 44; in relation to elec- tric potential, 44; in relation to respiration, 46; in axiate organs, 47, 220, 222; origin of new, 51, 70; obliteration of, 52; in limb rudiment of Amblystoma, 52; in animal egg, 54; in relation to hereditary protoplasmic consti- tution, 64, 129, 147; not pri- marily concerned in evolution, 66; originating in excitation gradients, 70, 77, 82, 235, 239; in Amoeba, 86; in the literature, 87; as an integrating factor, 89; in relation to differentiation, 90, 239; in relation to yolk develop- ment, 94; in relation to domi- nance and subordination, 97; in relation to direction of trans- mission, 97, 211, 213; in relation to physiological isolation, 102; in relation to localization of ner- vous structure, 108, 144, 148, 151, 153; in relation to definitely directed nerve growth, 112; ner- vous system primary develop- mental reaction to, 115; in relation to independence and dependence, 120; in relation to

Harenactis: origin of new polari- ties in, 52; bilateral tentacle groupings in, 57; axial integra- tion in, 248 Heredity: in establishment of axiate pattern, 49, 58, 59; gradi- ent conception independent of theories of, 66, 270 Heteromorphosis: axial, as normal feature of hydroid development, 34; axial, in Tubularia, 123; axial, in Planaria, 126 Hydroids: reversal of gradient in development of, 33, 243; origin of new polarity in, 52 Inhibition: differential, 36; de- velopmental results of, 37; microcephaly as differential, 37; cyclopia as differential, 38

Integration, organismic: nature of, 7, 15; possible quantita- tive factor in mechanism of, 10 ; in relation to chemical correlation, 13, 93; in relation to excitation-transmission, 89, 107; nervous system chief organ of, 89, 90, 108; in relation to electric current, 90; following physiological isolation, 105, 135; in relation to nervous centraliza- tion, 142; precedes appearance of nervous system, 144; incteno- phore plate row, 212; in reflex arc, 233; in higher vertebrates,

Isolation, physiological: in rela- tion to physiological dominance, 102; determined in four differ- ent ways, 103; dedifferentiation as result of, 103; in relation to agamic reproductive and repeti- tive processes, 104; in develop- ment of segments, 132; in development of branches of axon, 191; in ctenophore plate row, 217 Neuron: structure and develop- ment of, chaps, x, xi; of spinal ganglion, 166, 196; functional and developmental polarity of,

Organism: pattern and material of, i; simplest forms of, 4, 23 relation of, to external world, 7; spatial patterns of , 8; physiologi- cal correlation in, 10; as behav- ior pattern, 22, 268 Pattern, axiate: as one of three spatial patterns in organisms, 8; Pattern, bilateral: as one of three spatial patterns in organisms, 8; obliteration of, 56; origin of, 57; asymmetry in, 59. See also Symmetry Pattern, cell: as surface-interior pattern, 23, 61; nucleus as internal differentiation of, 61

Pattern, general: definition of, 2; distinction between, and mater- ial, 2, 270; in organism, 2; proto- plasmic, 5, 14; different orders of magnitude of, 5; chromosomal, 6, 18; types of, in organism, 8; excitation and transmission in, 16; relation between cytoplas- mic and nuclear, 19; of neuron compared with plant, 169. See also Pattern, organismic Pattern, neuronic: development and structure of, chaps, x, xi; in relation to chemo taxis, 170; as galvanotactic reaction, 171; in relation to electrical polariza- tion, chap, xi

Pattern, protoplasmic, 3. See also Pattern, general; Pattern, or- ganismic Pattern, radiate: as one of three spatial patterns in organism, 8; surface-interior pattern as, 23; repetition of parts in, 5 7. See also Pattern, organismic Pattern, surface-interior, 23, 61. See also Pattern, organismic. Permeability: gradients in, 40; in relation to susceptibility, 41; in relation to excitation, 72; in relation to origin of neuron pattern, 175 Planaria: susceptibility relations in, 34; external and internal gradients in, 35, 46; respiration gradients in, 47; biaxial heads in, 51; physiological dominance in, 100; physiological independ- ence of head region in, 121, 125, 126; central nervous system of,

Plants: physiological gradients in, 27, 29, 40, 47, 51, 53; determina- tion of polarity by light in, 51, 60; dominance and subordina- tion in, 99; physiological isola- tion in, 104; absence of nervous system in, 116; disappearance of physiological gradients in, Polarity, physiological, 24, 50. See also Dominance, physiologi- cal; Gradients, physiological; Pattern, organismic Polarization, electric: in relation to excitation, 72, 180; in rela- tion to neuron pattern, chap, xi; in relation to electro tonus, 180

Polyclads: reversal of suscepti- bility in, 34; limitation of regen- eration in, 134 Potential, electric: axial gradients in, 44; in relation to excitation, 70, 260; in relation to oxidation- reduction, 76, 180; in relation to neuron pattern, 173, 256, 258; in relation to development of cortex, 263. See also Polariza- tion, electric Receptors, position of, in relation to physiological gradients, no; in anaxiate form, 144; evolu- tionary change in position of peripheral, 151; in reflex arc, 233; in primitive gradient, 234; localization of, in relation to axes, 247, 249

Reduction, of KMnO4 in relation to physiological gradients, 42 Respiration: in relation to physi- ological gradients, 46; in Plan- aria dorotocephala, 47; in ground nervous tissue, 48 Reticulum, nervous: morphologi- cal character of, 156; develop- ment of pattern of, 202; func- tional direction in, 245 Self-differentiation: in embryonic development, 120; of head and apical region, 121; of central nervous system, 127 Stenostomum, physiological differ- ences in asexual and sexual stages of, 134

Subordination, physiological, 97. See also Dominance, physiologi- cal. Susceptibility: agents used in determining, 29; non-specific relation of, to physiological con- dition, 30, 36,40; gradients in, 32; changes in, during development, 33; specific, 34; of Planaria dorotocephala, 34; modification of development through differ- ential, 36; method of measur- ing, not exact, 38; in relation to permeability, 41; of embryonic heart, 48, 221; of alimentary tract, 48; of ctenophore plate row, 216; gradient in axon, 227; of excitation mechanism, 228

Symmetry: similarities of, in plants and animals, 2; radial and bilateral, 8, 25; spherical, 23; physiological gradients in bilat- eral, 28; as susceptibility gradi- ents, 33; bilateral, in siphono- phores, 33; origin of, 56; in relation to differentiation in general, 96; in relation to nerv- ous structure, no, 149; bilat- eral, in relation to dorsiventral- ity, 150. See also Pattern, bilateral; Pattern, cell; Pattern, organismic; Pattern, radiate

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