After extirpation of the thyroid gland prominent writers have found a diminution in the processes of oxidation; and by thyroid gland feeding we can augment these processes, as was shown by Vermehren, Magnus-Levy, Thiele, Nehring, and many others. This property of the thyroid gland is made use of in the medicinal treatment of obesity. Since writing these lines we have observed a loss of forty pounds in a man, a patient of Professor Launois, of Paris, who, after this loss, felt better. We treated him in Carlsbad for six weeks with thyroid extracts, and the average loss was about a pound a day. True, this patient was also taking Carlsbad water, but we have never seen so considerable a loss due to this water alone. The diet of this patient had not been strict. This loss of weight, then, is mainly to be ascribed to the thyroid treatment. This treatment is dangerous, however, unless carefully regulated by a physician. Thus extirpation of the thyroid is undoubtedly in causal relationship to obesity, which, as already mentioned, is often the first symptom of old age. But it also can produce another sign of old age, and this is the increase of connective tissue in the various organs and tissues. That connective tissue formation is an attribute of old age has been clearly shown by Demange and Oettinger, who found at every autopsy on old persons an increase of connective tissue in the walls of the capillaries. Ord and Mahomet found exactly the same thing in the capillaries of persons suffering from myxœdema. This has been proved experimentally by Professor Eiselsberg,[156] of Vienna, who found atheromatosis of the aorta and other blood-vessels in dogs whose thyroids he had removed. Footnote 156: “Die Krankheiten der Schilddrüse,” Stuttgart, 1901. This increase in connective tissue has been found in various viscera after removal of the thyroid; thus it was found by Kishi[157] in the liver of one hundred and fifty dogs and monkeys. Rosenblatt and Jeandelize[158] also described an interstitial hepatitis in similar cases. Footnote 157: Virchow’s Archiv, p. 260, 1904. Footnote 158: Loc. cit. The same change has also been noted in the kidneys after extirpation of the thyroid (e.g., Blum[159] found an interstitial nephritis), and in the brain an increase of neuroglia occurs, as observed by Blum, Walter Edmunds, and others. Footnote 159: Blum: Loc. cit. Increase of connective tissue in the skin is a common occurrence after thyroid extirpation, and the name “myxœdema” is probably derived from the fact that in some cases, as the disease advances, the connective tissue is transformed into a mucinoid substance. The name “cachexie pachydermatique,” as suggested by Charcot, seems to be far more adequate. Formation of fat and of connective tissue is not only seen after removal of the thyroid, but can also be observed after extirpation of the sexual glands, the ovaries and testicles.