NERVE. 



By Francis Gotch. 



Contents : — Fundamental Characteristics of Nerve Phenomena. — General 

 Review of Nerve Functions, p. 451 — Phenomena of the Excitatory State, p. 453 

 — Metabolism during Activity, p. 453 — Conductivity of Nerve, p. 455 — Trans- 

 mission in both Directions, p. 456 — The Excitation of Nerve. — Modes of 

 Stimulation, p. 459 — Induced Currents, p. 459— Undulatory Currents, p. 461 — 

 Condenser Discharges, p. 461 — Galvanic Currents, p. 462 — Unipolar Excitation, 

 p. 463 — Chemical Excitation, p. 464 — Mechanical Excitation, p. 467 — Condi- 

 tions determining the Efficiency of Stimuli, p. 468 — Law of Excitation, p. 469 

 — Influence of Direction of Electrical Currents, p. 472 — Nerve Indefatigability, 

 p. 473 — Limits of Excitation by Repeated Stimuli, p. 474 — The Circum- 

 stances affecting Nerve Excitability and Conductivity. — Maintenance of 

 Circulation, p. 477 — Maintenance of Continuity with Nerve-Cells, p. 478 — 

 Comparison of Different Nerves and Different Parts of same Nerve, p. 480 — 

 Alterations of Temperature, p. 484 — Chemical Reagents, p. 487 — Anaesthetics, 

 p. 491 — Polarisation Changes, p. 493 — Polar Excitation of Nerve by Elec- 

 trical Currents. — Pfluger's Law of Contraction, p. 503 — Influence of Duration, 

 etc., p. 505 — Causation of Polar Excitation, p. 507 — Closing and Opening 

 Tetanus, p. 510 — Polar Excitation in Crayfish Nerves, p. 512 — In Man, p. 515 

 — In Peripheral Sense Organs, p. 516 — Electromotive Changes in Unexcited 

 Nerve. — The Nerve Current, p. 518— Its Production, p. 519 — Influence of 

 Various Conditions on its Amount, p. 520 — Electro-motive Changes in 

 Excited Nerve. — The Negative Variation, p. 524 — Its Discontinuous Char- 

 acter, p. 527 — Electrical Response to One Stimulus, p. 529 — Influence of 

 Various Conditions, p. 533 — After-Effects, p. 537 — Electromotive Changes 

 associated with Passage of Currents. — External and Internal Polarisation, 

 p. 540 — Electrotonus, p. 546 — Influence of Physiological Changes upon Electro- 

 tonus, p. 550 — Excitatorv After-Effects, p. 556 — Polarisation and Excitation, 

 p. 557. 



The Fundamental Characteristics of Nerve Phenomena. 



G-eneral review of nerve functions. — The physiological phenomena 

 exhibited by nerve may be considered under three different aspects, 

 indicated by the terms " excitability," " conductivity," and the " state of 

 excitation." 



Excitability is pre-eminently the attribute of nervous tissue ; hence 

 the phenomena of nerve comprised under this expression represent more 

 definitely than those of other excitable structures the conditions which 

 determine its possession, and the circumstances which modify its mani- 

 festation. A tissue is said to be excitable if it responds by the develop- 

 ment of specific changes to the local action of external change in its 

 immediate environment. The altered condition thus produced is termed 

 " the excitatory state," whilst the external agent which lias evoked this 

 is termed the " stimulus " or " exciting cause." 



