Stomach of a Bird
The stomach of a grain-eating bird, which has a gizzard that functions to crush the seeds to pieces since birds have no teeth to crush their food. It has on its inside two hard surfaces which rub and press against each other by muscles to grind food. At b is the gizzard cut open, showing two hard grinding surfaces, and at a above is the part from which oozes the gastric juice.
Hooker, Worthington First Book in Physiology For the Use of Schools and Families (New York: Sheldon and Company, 1867) 35