We have also frequently seen a marked improvement in the mental faculties of adults through thyroid treatment. Thus last winter, during a stay in Nice, we were consulted by an American lady of 69 years who was suffering from arteriosclerosis and dizziness. Through thyroid treatment the intelligence of this lady improved so much that it became very noticeable to her English trained nurse, who told us that whereas before she could do anything with this mentally torpid woman without comment, now she first demanded to know the reason for everything before she complied with the dietary and hygienic measures the nurse wanted her to follow. That the thyroid gland affects the intellect is also proved by the very important fact that the serum of animals whose thyroid has been extirpated, and which is thus antagonistic to the thyroid gland, is able to impair the intellect. Dürig[92] noticed this after using large doses of such serum in a woman with Graves’s disease, thereby causing an appearance of great stupidity, loss of memory, and incapability of thinking, so that he had to suspend the treatment. These symptoms continued for fourteen days after the treatment had been discontinued. Footnote 92: Dürig: Münchener Med. Woch., 1908, Nu. 18. Sleep is also one of the functions controlled by the thyroid, and as its changes are able to promote senility, we believe it will be well to discuss this more fully in a special chapter (XLIII). We cannot recall any alteration of the thyroid gland that is not accompanied by nervous symptoms. In Graves’s disease (exaggerated activity of the thyroid) we observe a condition of great nervousness, so much so that, according to some authorities, Graves’s disease may be termed a neurasthenia with tachycardia. There are many women treated for simple hysteria who are, in fact, suffering from a partial form of Graves’s disease with its cardinal symptom: tachycardia. In cases of Graves’s disease we often find conditions of exaltation, even manias, and very frequently, at the very least, great irritability. On the other hand, in myxœdema there is, usually, a condition of melancholia, and it is interesting in this connection, that in a number of cases of melancholia we have found a swelling of the thyroid with a cessation of the menstrual flow; such cases improved after thyroid treatment, particularly when conjoined with treatment by ovarian extracts. In the lunatic asylum of Pontiac, Michigan, some 100 cases of swelling of the thyroid have been traced out of 600 insane inmates, as we heard on the occasion of our visit to our friend, Dr. Edwin S. Sherril, of Detroit, four years ago.