Page:Popular Science Monthly Volume 30.djvu/645

Rh teeth, some had been without them many years, and the average number retained was only four or five, which, in many instances, we may conclude to have been of little value. The artificial substitutes were used in so few instances, that we can not from them form an estimate of the aid afforded by these appliances in the prolongation of life; but that they do contribute to the maintenance of health and the prolongation of life can scarcely be a matter of doubt. The teeth had disappeared, as we have before found to be the case ("British Medical Journal," May 9, 1885, page 929) in the upper jaw more than in the lower; but the tables do not show so much difference between the men and the women as I then marked.

It is somewhat remarkable that, though as many as twenty-eight used glasses, thirty-five, including many who used glasses, are reported to have been in the enjoyment of good sight. The occurrence of presbyopia does not seem to be associated with, or to be a prelude to, inconvenience or impairment of sight beyond that which may be corrected by glasses. These had been used by some for forty or fifty years; and in three it appears that the defect was spontaneously rectified, and that as they grew older they became able to dispense with glasses.

That the majority of centenarians are content, as we find them to be, with three meals in the day, and are moderate or small eaters, partaking of little animal food and little alcohol, is in harmony with the lowered activity of the muscular and other organs, and the consequent lowered demand upon the nutritive processes and the nutritive supply. That nevertheless the rate of the pulse, averaging 70, and that of the respiration, averaging 23, is maintained, may be accounted for by the diminished elasticity of the circulatory and respiratory apparatus. The arteries become less capable of accelerating the bloodstream, and the vital capacity of the chest is much reduced, as shown by the slight difference in the chest-girth between the state of inspiration and that of expiration.

The sleep-duration, averaging nearly nine hours, indicates also a slowness, a feebleness, of the restorative processes. Repair is tardily and with difficulty striving to keep pace with wear. We know that it is one element in the developmental law of growth and decay, that it should not quite do so in the aged frame. Up to adolescence repair has the mastery, and the body gains in weight and strength; in middle age, repair is about equal to wear; but in later life its gradual failure, attended with diminishing weight and strength, conducts the body slowly along its normal course to dissolution. Long, good sleep, does something to put a drag on the downward course, and is a great sustainer of the aged frame. Much difference in sleep-duration is noted in the tables. In some, sleep is said to have been short and indifferent, or bad, perhaps owing to peculiar disturbing causes; but in 33 out of 44 it is said to have been good.

The maladies of these old people range themselves chiefly under