The Lymphatic Vessels of the Thyroid Gland in the Dog and in Man

The lymphatics of the thyroid have been referred to as the ducts of the gland. This reference originated in 1836, when King and Cooper1claimed to have observed colloid in the lymphatic vessels within the thyroid and also as they left the gland. Since that time the lymphatic drainage of the thyroid has been the subject of a great deal of controversy. This difference of opinion has arisen mainly because with the customary technic of injecting the lymphatics of parenchymatous organs by needle puncture there was uncertainty as to which channels have been injected—lymphatics, capillaries or tissue spaces. There is now a general agreement on the fact that the external surface of the thyroid is covered by a rich anastomosing plexus of lymphatic vessels and on the course of the larger extraglandular collecting trunks that drain the plexus. However, the relation of the lymphatic capillaries to the definitive histologic