8, 14).

Imperfect development or absence of this organ, or an inactive condition of it, produces in the child arrested growth and deficient mental development known as cretinism, and in the adult the same condition gives rise to mental deterioration, swelling of the skin, due to a greater content of water, and loss of hair.

This deficiency in the production of thyroid secretion can be made good and the symptoms removed by feeding the patient with similar glands removed from animals.

The very complex disease known as exophthalmic goitre, and shown by irregular and rapid action of the heart, protruding eyeballs and a variety of mental symptoms, is also associated with this gland, and occasioned not by a deficiency but by an excess or perversion of its secretion.
Adjoining the thyroid there are four small glands, the parathyroids, each about the size of a split pea.

The removal of these glands in animals produces a condition resembling acute poisoning accompanied by spasmodic contraction of the muscles.