DURING the past 346 years the thymus has many times been convicted and acquitted of causing obstructive symptoms and death in infants, children, and adults. Since 1858, when Friedleben first doubted Kopp's obstructive theory, there have been two sides to this argument, and the courts are still in session. It is the purpose of this paper to review the theories by which the thymus has been maligned, analyze their fundamental structure briefly, relate an experience of ours with reference to the current concepts of the thymus, present evidence against the obstructive theory, and to suggest a possible viewpoint to be taken by the physician when confronted with this problem.
Five principal theories have been proposed concerning how the thymus produces symptoms and death: The first, the obstructive theory by which the thymus produces mechanical pressure on the trachea, blood vessels, and nerves, principally the recurrent laryngeal and vagus. The second,