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Current of injury

The current of injury, also called the injury current or demarcation current, flows between an injured point of living tissue and an uninjured one. Early physiologists used it as a baseline for reading excitation, because stimulation reduced it, a change called the negative variation.1 Later authors tied it to membrane permeability3 and to the currents that flow from wounds and amputations.8

Earliest held
1852, Du Bois-Reymond, E. (ed. H.…
Most discussed in
Comparative Electro-Physiology: A…, 1907
In the library
224 passages in 16 works
Rewritten
2026-10-04
18501875190019251950197520002025Bose, J. C., 19021Bose, J. C., 19072Bayliss, W. M., 19153Lillie, R. S., 19234Lillie, R. S., 19235Bose, J. C., 19266Bose, J. C., 19287Tyler SEB, 20178O'Hara-Wright M, Mobini S…, 20229
01

Early work on nerve

Du Bois-Reymond's arrangement for observing the negative variation: a frog muscle across two pads, led to a galvanometer.
Du Bois-Reymond's arrangement for observing the negative variation: a frog muscle across two pads, led to a galvanometer. Wikimedia Commons, CC BY-SA 4.0

Bose (1902) treated the current of injury as the baseline against which excitation is read. He argued that stimulation reduces the existing difference of potential, so a nerve shows a negative variation. He described this as a current of action opposed to the current of injury, running from the more excited region to the less excited one.1 He also noted that some physiology textbooks had drawn wrong inferences by supposing the injured end to be zinc-like.1 Bose (1907) reported that the same excitatory reaction could give opposite signs. With slight injury the response was a negative variation. When the injured point was killed, the injury current reversed and the response was a positive variation.2

02

Membrane explanations

Bayliss (1915) gave a membrane account. He wrote that excitation is accompanied by increased permeability of the cell membrane.3 If the membrane is impermeable at rest to one ion only, it is polarised, and the current of rest is accounted for. Loss of that semipermeability in excitation then accounts for the negative variation.3 Lillie (1923) reported Hober's finding that potassium, rubidium and ammonium salts produce an injury current in muscle, while sodium and lithium salts leave the surface potential unchanged.4 Lillie put the maximum change during contraction near 0.05 volt, similar to the demarcation current. He added that some observers found larger action potentials, up to 0.08 volt.5

03

Injury as a method

Bose also used injury as an experimental tool. In The Nervous Mechanism of Plants (1926) he described abolishing the excitability of one contact by local injury, so that the response at the other contact is not opposed. This produces a current of injury, and the response appears as a negative variation of it.6 The injured tissue may recover, which shrinks the response, so a fresh injury must be made.6 In The Motor Mechanism of Plants (1928) he described the animal method in the same terms. The injured point is negative, and the response disappears as the current of injury subsides.7

04

Wound currents today

Recent reviews place the current of injury within work on regeneration. Tyler (2017) reported that wounding human skin generates an injury current, typically 1 to 10 μA/cm2, citing Nuccitelli. Amputated newt limbs gave 10 to 100 μA/cm2, and newly amputated human fingertips gave 22 μA/cm2.8 Tyler noted the suggestion that regenerating and non-regenerating systems differ in their bioelectric characteristics.8 O'Hara-Wright and colleagues (2022) described the injury potential as a difference between intact epithelium and the wound. Current leaks from the wound edge as the path of least resistance and creates an electric field.9

SourcesEach quotation was checked word for word against the passage it opens.
  1. and acted in an opposite direction to the current of injury (fig. 2,4). The action current in the nerve is from the relatively more excited to the relatively less excited.Bose, J. C., 1902 · Response in the Living and Non-Living · open at passage 30
  2. It will thus be seen that an identical excitatory reaction of the living tissue appears to give rise to directly oppositeBose, J. C., 1907 · Comparative Electro-Physiology: A Physico-Physiological Study · open at passage 479
  3. There is evidence that the state of excitation is accompanied by increased permeability of the cell membrane.Bayliss, W. M., 1915 · Principles of General Physiology · open at passage 1884
  4. produce an injury-current or local negativity. Absence of penetration is indicated by failure to change the external potential of the muscleLillie, R. S., 1923 · Protoplasmic Action and Nervous Action · open at passage 279
  5. The maximum range of variation during contraction does not usually appear to exceed 0.05 volt, a potential-difference similar to that of the demarcation-current.Lillie, R. S., 1923 · Protoplasmic Action and Nervous Action · open at passage 537
  6. This method introduces several complications: a current of injury is produced, and the response at A is then observed as a negative variation of the current of injury.Bose, J. C., 1926 · The Nervous Mechanism of Plants · open at passage 232
  7. Then the current of injury gradually subsides, with the result of disappearance of response by negative variation.Bose, J. C., 1928 · The Motor Mechanism of Plants · open at passage 374
  8. Immediately upon wounding human skin, an endogenous ionic flux generates the so-called injury current, typically between 1 and 10 μA/cm2Tyler SEB, 2017 · Nature's Electric Potential: A Systematic Review of the Role of Bioelectricity… · open at passage 19
  9. Known as the injury potential, or demarcation current, a difference in electrical potential is created between intact epithelium and the site of a woundO'Hara-Wright M, Mobini S, Gonzalez-Cordero A, 2022 · Bioelectric Potential in Next-Generation Organoids: Electrical Stimulation to… · open at passage 19
Linked ideas
Resting membrane potentialprecursor of / follows
Bayliss explains the injury current and its negative variation through a polarised membrane that is selectively permeable at rest; Lillie gives demarcation potentials in volts.
Tyler cites the proposal that regenerating and non-regenerating systems differ in bioelectric characteristics, pointing to wound currents as one measured example.
Galvanotaxisrelated to
Funk links electric-field guidance of cell migration to wound healing and regeneration; McMillen et al. compare tumor disruption of transepithelial potential to epithelial wounding.
Bose (1902) obtains electric response by the method of injury and lists current of injury among the conditions for it.
McMillen et al. say tumour formation disrupts transepithelial potential in a process akin to epithelial wounding.
Bayliss attributes the negative variation to loss of membrane semipermeability in excitation, so the resting polarisation falls and the injury current diminishes.
Regenerationrelated to
Tyler and O'Hara-Wright report injury current at wounds and amputations, with higher currents in amputated newt limbs and regenerating child fingertips.
Bayliss and Lillie reason from ion permeability of the membrane, the same question later framed in terms of channels, though the passages do not use that term.
Lillie read salt effects on the demarcation potential as evidence of which ions penetrate resting muscle.
Osterhout linked injury and death to conductivity change, which connects antagonism to electrical signs of damage.
Bose described the action current as a positive or negative variation of the injury current, and fatigue could reverse it.
Another bioelectric current of living tissue, discussed alongside the action current of the approaching excitation wave.
Wound-induced potentials at the cathode in epithelia act as a guiding signal for migration, as reviewed by Funk.
Where it is discussedPassages matching current of injury, injury current, demarcation current, negative variation
1907Comparative Electro-Physiology: A Physico-Physiological Study · Bose, J. C.112
1902Response in the Living and Non-Living · Bose, J. C.37
1852On Animal Electricity: Being an Abstract of the Discoveries of Emil du… · Du Bois-Reymond, E. (ed. H. Bence Jones)17
1906Plant Response as a Means of Physiological Investigation · Bose, J. C.13
1915Principles of General Physiology · Bayliss, W. M.13
1923Protoplasmic Action and Nervous Action · Lillie, R. S.11
1918Life Movements in Plants · Bose, J. C.9
1928The Motor Mechanism of Plants · Bose, J. C.3
1926The Nervous Mechanism of Plants · Bose, J. C.2
2017Nature's Electric Potential: A Systematic Review of the Role of Bioelectricity… · Tyler SEB1