BioelectricaAlterspan Labs
Bioelectricity  ·  Article

Galvanic current, muscle tension and electrical orientation of swimming (galvanotropism in animals)

Galvanotropism is the forced orientation of an animal in a galvanic current. Jacques Loeb studied it in the shrimp Palaemonetes and argued that the current alters the tension of antagonist muscles, so that movement toward one electrode becomes easy and movement toward the other becomes hard12. He treated it as a physical process, not a purposeful behaviour7.

Earliest held
1900, Loeb, J.
Most discussed in
Forced Movements, Tropisms, and Animal Conduct, 1918
In the library
55 passages in 11 works
Rewritten
2026-11-06
18501875190019251950197520002025Loeb, J., 19001Loeb, J., 19002Loeb, J., 19063Bose, J. C., 19064Loeb, J., 19065Loeb, J., 19166Loeb, J., 19187Pietak A, Levin M, 20168Gershman SJ, Balbi PE, Gallistel CR…, 20219
01

The shrimp experiments

In 1900 Loeb described what happens when a current is sent through Palaemonetes from head to tail. The swimming appendages and the tail are stretched backward to their fullest extent1. He took this to show that the muscles moving those organs backward have more tension than their antagonists1. The shrimp then swims toward the anode easily and backward only with difficulty2. When the current runs from tail to head, the appendages turn forward and the animal swims backward easily1. Loeb also noted that the tail fin behaves like the abdominal appendages and not like the body1.

02

Orientation and locomotion

In 1906 Loeb separated two effects of the current. Sessile organs show only a galvanotropic curvature3. Wherever the current affects the locomotive organs of a free-swimming animal, swimming toward the cathode or the anode must occur as well as the orientation3. Loeb cited the infusorian Paramecium as an example3. In the same year Bose reported work by Greely on Paramecium. Alkali-reared animals invariably first swam toward the kathode, while acid-reared animals generally did the reverse4. Bose linked this to the opposite effects of acids and alkalis4.

03

A mechanical theory

By 1918 Loeb stated the theory in general form. All galvanotropic phenomena were reduced to changes in the tension of associated muscles or contractile elements7. Galvanotropism was therefore a forced motion, produced by the current instead of by injury to the brain7. He then asked how a current produces such changes. He answered that currents pass through tissue as ions, and that membranes more permeable to some salts than to others block their progress7.

04

Use, selection and later reading

Loeb used galvanotropism as an argument against explaining tropisms by natural selection. He held that it is purely a laboratory phenomenon, since no animal meets such a current outside the laboratory, yet it is common56. In 1916 he said this puzzled the selectionist, the Lamarckian and the vitalist alike6. Gershman and colleagues (2021) describe Loeb's tropism view as influential in early protozoan study. They say he and his students treated many movements as reactions to an asymmetric force8. Pietak and Levin (2016) list galvanotropism of cells as a missing component among the current limitations of their BETSE model9.

SourcesEach quotation was checked word for word against the passage it opens.
  1. This proves that the tension of the muscles that move those organs back- wards is greater than that of their antagonists.Loeb, J., 1900 · Comparative Physiology of the Brain and Comparative Psychology · open at passage 248
  2. The shrimp can thus swim forwards toward the anode easily under the influence of such a current, but back- wards only with difficulty.Loeb, J., 1900 · Comparative Physiology of the Brain and Comparative Psychology · open at passage 248
  3. Wherever the current affects the locomotive organs of a free- swimming animal, besides the galvanotropic orientation of the animal, a swimming either toward the cathode or anode must occur.Loeb, J., 1906 · The Dynamics of Living Matter · open at passage 384
  4. Greely has found that while alkali-reared Paramcecia invariably give the initial response by swimming towards the kathode, the reverse is generally the case with those which have been subjected to acidBose, J. C., 1906 · Plant Response as a Means of Physiological Investigation · open at passage 1616
  5. Galvanotropism is purely a laboratory phenomenon; outside of the laboratory no animal ever comes into a situation which might call forth a galvanotropic reactionLoeb, J., 1906 · The Dynamics of Living Matter · open at passage 425
  6. galvanotropism is purely a laboratory product and no animal has ever had a chance or will ever have a chance to be exposed to a constant current except in the laboratory of a scientist.Loeb, J., 1916 · The Organism as a Whole, from a Physicochemical Viewpoint · open at passage 484
  7. All the phenomena of galvanotropism are, therefore, reduced to changes in the tension of associated muscles or contractile elements, as a consequence of which the motion of the organism toward one pole is facilitatedLoeb, J., 1918 · Forced Movements, Tropisms, and Animal Conduct · open at passage 68
  8. galvanotaxic movement of cells and galvanotropism in response to endogenous, global electric fields, is another key component of bioelectric pattern regulationPietak A, Levin M, 2016 · Exploring Instructive Physiological Signaling with the Bioelectric Tissue… · open at passage 139
  9. Loeb and his students applied this concept more broadly to algae and animals, arguing that many movements could be conceptualized as reactions to an asymmetrically impinging forceGershman SJ, Balbi PE, Gallistel CR, Gunawardena J, 2021 · Reconsidering the evidence for learning in single cells · open at passage 10
Linked ideas
Galvanotaxisrelated to
The movement of cells and organisms in an electric field, of which the shrimp's swimming toward the anode is an animal case.
Tropismpart of / contains
Galvanotropism is one of the tropisms, alongside heliotropism, in Loeb's scheme of forced reactions to asymmetric forces.
Loeb called galvanotropism a forced motion produced by the current instead of by brain injury.
Loeb compared galvanotropism with heliotropism as phenomena of the same category, differing mainly in that the current reaches all cells.
Loeb argued that galvanotropism, a purely laboratory reaction, speaks against explaining tropisms by natural selection.
Paramecium and Volvox were used to test whether galvanic and light reactions share a mechanism.
Where it is discussedPassages matching swimming toward the anode, current through the animal head to tail, tension of the muscles antagonists, galvanotropism
1918Forced Movements, Tropisms, and Animal Conduct · Loeb, J.14
1906The Dynamics of Living Matter · Loeb, J.10
1900Comparative Physiology of the Brain and Comparative Psychology · Loeb, J.9
1912The Mechanistic Conception of Life · Loeb, J.6
1916The Organism as a Whole, from a Physicochemical Viewpoint · Loeb, J.5
1906Behavior of the Lower Organisms · Jennings, H. S.3
1906Plant Response as a Means of Physiological Investigation · Bose, J. C.3
1923Protoplasmic Action and Nervous Action · Lillie, R. S.2
2016Exploring Instructive Physiological Signaling with the Bioelectric Tissue… · Pietak A, Levin M1
2021Reconsidering the evidence for learning in single cells · Gershman SJ, Balbi PE, Gallistel CR…1