Emily Dickinson Lexicon

THY'MUS, n. [Gr. θυμος.]

In anatomy, a glandular body, divided into lobes, situated behind the sternum in the duplicature of the mediastinum. It is largest in the fetus, diminishes after birth, and in adults often entirely disappears. It has no excretory duct, and its use is unknown. In calves it is called sweet-bread; but the term sweet-bread is also applied to the pancreas, a very different organ. Hooper. Wistar. Parr.