THE thyroid gland consists of saccules of various shapes lined with "epithelium. In these saccules there is often a little clump of colloid matter, the amount of which varies within normal limits. The gland has no duct, and its secretion presumably passes into the blood by the lymphatics or the veins. This secretion has evidently a most important function in the animal economy as excision or atrophy of the gland leads to a serious train of symptoms (see under Myxcedema).