Electro-galvanic ring.
Licence: Attribution 4.0 International (CC BY 4.0)
Credit: Electro-galvanic ring. Wellcome Collection. Source: Wellcome Collection.
![no text alternative](https://iiif.wellcomecollection.org/image/L0004524/full/800%2C/0/default.jpg)
Licence: Attribution 4.0 International (CC BY 4.0)
Credit: Electro-galvanic ring. Wellcome Collection. Source: Wellcome Collection.