Constipation or irregularity of the bowels is also common. There is often great fatigue, slow speech, and an apathetic condition in both these states. The memory shows the same typical deficiency, events of long ago being more easily remembered than those of quite recent date. The character of the patient becomes egotistical and avaricious. There is great sensibility to cold and difficulty in keeping warm. The urine is generally below the normal quantity; often it is scanty and of low specific gravity, with retention of solid constituents. The processes of oxidation are diminished both in typical myxœdema and in advanced old age. There is a diminution of the blood-corpuscles and of hæmoglobin in both conditions. After the initial obesity in early myxœdema and old age, there comes as a second stage a loss of fat, characteristic of the advanced stage of myxœdema (the cachectic stage) and advanced old age. There is an increase of fatty tissue after extirpation of the thyroid gland, and later of connective tissue, just as in myxœdema and old age. This increase of connective tissue is typical of old age. It first appears in the arteries, leading to atheroma, and the typical symptoms of arteriosclerosis. In myxœdematous persons, although they may still be young, we find atheromatous arteries and arteriosclerosis. Impotence is common in myxœdema, especially in advanced cases, and is also found in senility, being more marked the greater the patient’s age. There is no denying the fact that in old age we find, besides degeneration of the thyroid, symptoms of degeneration in various other tissues and functions, and the question now arises, whether these changes in the tissues are really the sequel of previous degeneration of the ductless glands, or whether both are only accidental and in no causal relation We have already answered this question four years ago in our communication to the Paris Biological Society, showing that old age is due to degeneration of the ductless glands, and stating that these glands govern the tissues and not _vice versa_. Still, we shall enter here more fully upon this question, showing by experimental and clinical evidence that the changes in the ductless glands are primary, and followed by a degeneration of the tissues as a consequence. We can produce experimentally typical symptoms of old age in young animals by extirpation of the ductless glands, more especially the thyroid, ovaries, and testicles. When we extirpate the thyroid gland of an animal we get an increase of fat in the subcutaneous tissue, or an increase of connective tissue. We know of the case of a young bull which, two months after extirpation of the thyroid, gained about thirty kilos in weight, due to an increase in fat. The same thing occurred in a colt. We are indebted for our knowledge of both these cases to Dr. Hertoghe, of Antwerp, the well-known authority on the thyroid gland.