"A frog battery is an electrochemical battery consisting of a number of dead frogs (or sometimes live ones), which form the cells of the battery connected in a series arrangement. It is a kind of biobattery. It was used in early scientific investigations of electricity and academic demonstrations.
The principle behind the battery is the injury potential created in a muscle when it is damaged, although this was not fully understood at the time; the potential being caused incidentally due to the dissection of the frog's muscles.
The frog battery is an example of a class of biobatteries which can be made from any number of animals. The general term for an example of this class is the muscular pile."