Intern. Congr. of Med., Madrid, April, 1903; and various Addresses to the Brussels Royal Society for Med. and Nat. Sciences, 1903, the Hamburg Med. Society, 1904, the Paris Biolog. Society, 1904, the London Path. Society, 1905, etc. Footnote 3: Sajous: “Internal Secretions and the Principles of Medicine,” vol. i, 1903, and vol. ii, 1907, and Philadelphia Medical Journal, March 7, 1903. The most important part herein is taken by the thyroid gland, whose increased activity is followed by an augmentation of the processes of oxidation in the body, whereas its degeneration is followed by a diminution of these processes. When the thyroid gland is degenerated entirely, as in myxœdema, there is also a great diminution of all oxidation processes. There are also cases where the thyroid is only partially altered by the increase of connective tissue, cases called partial myxœdema, and in these cases, accordingly, the diminution of the processes of oxidation does not take place to the same extent as in complete myxœdema. When we thus find symptoms of old age in young persons, together with, in the most typical cases, a state of decreased oxidation, we have to determine whether or not we are dealing with a degeneration of the thyroid gland. And, indeed, such a condition is before us, for the symptoms we have just mentioned are characteristic of myxœdema. If complete myxœdema, the highest degree of this condition, is rare, on the other hand the incomplete forms, where the thyroid is only partially replaced by connective tissue, are fairly common. This is shown by the fact that, after the fortieth or forty-fifth year, the thyroid shows an increased amount of connective tissue, and thus cannot be so active as a thyroid with more secreting elements and less connective tissue. We have thus reasons to suppose that the persons above mentioned, who only exhibit some but not all of the symptoms of old age, symptoms which are also found as typical in myxœdema, are suffering from a partial myxœdema or hypothyroidia. And it does not necessarily follow that in all such cases the processes of nutrition will be diminished, as is the rule in typical cases of myxœdema. The resemblance between senility and myxœdema was first pointed out in 1890 by Sir Victor Horsley, one of the foremost authors on myxœdema, and afterward by Vermehren,[4] Ewald,[5] of Berlin, and the author. Horsley ascribed old age to degeneration of the thyroid gland, and we have shown (in a communication to the Paris Biological Society, presented by Dr. Gley, Professor of Physiology at the University of Paris, December 4, 1904) that, besides the thyroid, there are also different other ductless glands whose degeneration produces old age. These are the sexual glands, the pituitary body, and the adrenals. Footnote 4: Over Myxœdemet, Kjöbenhavn, 1895. Footnote 5: Ewald: “Die Erkrankungen der Schilddrüse,” Nothnagel’s Handbuch, Vienna, 1896.