thymus

The thymus gland attains a considerable development in the embryo and shrinks away to the merest vestige in the adult.

Owen says that the thymus appears in vertebrates with the establishment of the lung as the main or exclusive respiratory organ.

The enlargement or persistence of the thymus can be better recognised, and doctors now seldom fail to notice it.

It is nearly always accompanied by a distinct hypertrophy of the thymus gland.

The thymus gland, which lies near the heart and is often called the heart sweetbread, is the best one.