THYROID

(Greek Thuroeides, ‘shield shaped’), term applied to the largest eartilage of the larynx, and also to the large ductle gland on the lower part of the front of the neck; a two-lobed structure connected by an isthmus acro the front of the trachea. The gland is well supplied by blood-ve els, the most important being the superior thyroid artery, a branch of the external carotid. The gland is composed of minute cavities, lined with cubical cells, and filled with an insoluble gelatinous material, while in the walls of the cavities the small blood-ve els anastomose freely. The function of the gland is not yet precisely known, but it has been shown that if it is excised mucous degeneration is produced in various ti ues of the body, accompanied by derangement of the nervous system. Myxoedema and Cretinism are conditions due to absence or great diminution of the gland or its internal secretion, while in the condition of Goitre the gland is enlarged. Preparations are made from the fresh or dried gland and used medicinally in the treatment of the above conditions. The experiments of Veronoff (1913 seq.) in treating thyroid deficiency in children by grafting the thyroid gland from apes attracted much attention in 1920, as also did his further experiments to counteract the natural advance of old age. TRACA.