Animal Glue

An animal glue is an adhesive that is created by prolonged boiling of animal connective tissue.

These protein colloid glues are formed through hydrolysis of the collagen from skins, bones, tendons, and other tissues, similar to gelatin. The word "collagen" itself derives from Greek κόλλα kolla, glue. These proteins form a molecular bond with the glued object.

Stereotypically, the animal in question is a horse, and horses that are put down are often said to have been "sent to the glue factory." However, other animals are also used, including rabbits and fish.