We should like to add that, as the above agencies are also harmful to the thyroid gland, the antagonist of the adrenals, its degeneration can further the development of arteriosclerosis in the same way that Eiselsberg produced an atheromatosis of the aorta in dogs after extirpating the thyroid gland. According to Minnich, arteriosclerosis is very common in people with goiter, appearing in them at a very early age. Fries and Pineles found that alterations of the blood-vessels occurred in goats after extirpation of their thyroid gland. Since arteriosclerosis is so frequent in old age it must be due to the degeneration of the thyroid and also to the aggregation of all the above-named harmful agencies during a prolonged period. To avoid it, and also premature old age, it is, therefore, most essential to guard against all agencies harmful to the thyroid and adrenals, to which we have referred above; and this is the best basis for the rational treatment of arteriosclerosis. It is most fortunate that Dellamare discovered in old age a hypertrophy of the adrenals.[208] Footnote 208: “Recherches sur la senescence des glandes surrénales,” Soc. biologie, 17 Oct., 1903. All this is greatly strengthened by the recent investigations of Sajous, which show that besides its action on the blood-pressure and the heart, the adrenal secretion actually supplies the substance which in the lungs, takes up the oxygen from the air to sustain life in all our tissues. It thus becomes evident that harm to our adrenals is bound to shorten life. To recapitulate: There exist two chief agencies for the production of arteriosclerosis: 1. A hyperactivity of the adrenals, causing a rise in blood-pressure. 2. A degeneration of the thyroid gland, which, when normal, antagonizes the first by lowering the blood-pressure. Although from the above-mentioned facts high blood-pressure cannot be considered as the chief cause of arteriosclerosis, still no doubt it certainly contributes to it; for each time that there is a rise in the blood-pressure more blood is forced through the arteries, thereby causing them to dilate; and after a repeated number of such dilatations the elasticity of the vessels will eventually be impaired, especially so in the aged, where one part of the elastic fibers is already replaced by connective tissue. As a result of the arteriosclerosis the passage of blood through the capillaries will be impeded, and in consequence the work of the heart will be increased; likewise the nutrition of the walls of the vessels will be diminished. The best preventatives of arteriosclerosis will therefore be: 1. To avoid all agencies which may tend to cause excessive activity of the adrenals; and 2. To increase the activity of the thyroid.