the current necessary to hold membrane voltage constant at a commanded value. A silver wire, inserted into the interior of the axon, forces a constant membrane voltage along the length of the axon. Under these circumstances, there is no possibility of a traveling 'soliton'. Any thermodynamic changes are very different from those resulting from an action potential. Yet, the measured currents accurately reproduce the action potential. Single channel currentsThe patch clamp technique isolates a microscopic patch of membrane on the tip of a glass pipette. It is then possible to record currents from single ionic channels. There is no possibility of propagating solitons or thermodynamic changes. Yet, the properties of these channels (temporal response to voltage jumps, ionic selectivity) accurately predict the properties of the macroscopic currents measured under conventional voltage clamp. Selective ionic conductivityThe current underlying the action potential depolarization is selective for sodium. Repolarization depends on a selective potassium current. These currents have very specific responses to voltage changes which quantitatively explain the action potential. Substitution of non-permeable ions for sodium abolishes the action potential. The 'soliton model' cannot explain either the ionic selectivity or the responses to voltage changes. Pharmacology The drug tetrodotoxin (TTX) blocks action potentials at extremely low concentrations. The site of action of TTX on the sodium channel has been identified. Dendrotoxins block the potassium channels. These drugs produce quantitatively predictable changes in the action potential. The 'soliton model' provides no explanation for these pharmacological effects. Action waves A recent theoretical model, proposed by Ahmed El Hady and Benjamin Machta, proposes that there is a mechanical surface wave which co-propagates with the electrical action potential. These surface waves are called "action waves". In the El Hady–Machta's model, these co-propagating waves are driven by voltage changes across the membrane caused by the action potential. See also Biological neuron models Hodgkin–Huxley model Vector soliton Sources Federico Faraci (2013) "The 60th anniversary of the Hodgkin-Huxley model: a critical assessment from a historical and modeler’s viewpoint" Revathi Appali, Ursula van Rienen, Thomas Heimburg (2012) "A comparison of the Hodgkin-Huxley model and the Soliton theory for the Action Potential in Nerves " Action Waves in the Brain, The Guardian, 1 May 2015. Ichiji Tasaki (1982) "Physiology and Electrochemistry of Nerve Fibers" Konrad Kaufman (1989) "Action Potentials and Electrochemical Coupling in the Macroscopic Chiral Phospholipid Membrane". Andersen, Jackson and Heimburg"Towards a thermodynamic theory of nerve pulse propagation" Revisiting the mechanics