The Thyroid Gland

The lateral lobes of the thyroid gland are long and narrow, and have a flattened, ellipsoidal form; they are placed on the lateral surfaces of the trachea near the larynx. The extremities are small, the posterior one often being pointed. The isthmus is inconstant and variable; in large dogs it usually has the form of a glandular band which may be nearly half an inch (ca. 1 cm.) wide; in small dogs it is usually absent.

Accessory thyroids are frequently present; three or four may be found on either side, as well as a median one near the hyoid bone.

The parathyroids, about the size of millet or hemp seed, are four in number usually. Two are placed on the deep face of the thyroid lobes; the others are placed laterally near the anterior extremity of the thyroid.