Probably no organ of the body has been more discussed and less understood than the thymus gland. Uncertainty exists whether the gland should be classified with the lymphoid tissues or as an endocrine organ. There has been no general agreement on its function nor on its activity as a lymphopoietic organ. The only feature that has not changed since the second century AD is its name; Galen recognized its resemblance to flowering thyme and named it accordingly. Until recently there had been little experimental work to support even the most reasonable speculations and deductions.
During the last decade, however, knowledge of the thymus has been advanced by sound experimental studies, especially important in oncology. The role of the thymus in lymphopoiesis and its endocrine functions have been of paramount interest. Recently Osoba and Miller1 have concluded from animal experiments that a thymic humoral factor exists which enables the lymphoid