in out-of-the-way places or where older and more differentiated cells would be expected should excite suspicion. “Young cells, like young children, are safest among their own.” Generally a cell in an organism lives long enough to reproduce its kind; else the species would die and death does occur in many lower organisms immediately after ovulation. The young thus grow rapidly, while old age is the period of slowest growth; and indeed the rate of growth depends upon the degree of senescence. The tendency to senescence is at its maximum in the very young and the rate of senescence diminishes with age. As to the cause of senility, physiologically it is desiccation. At birth there is most fluid and gaseous material, but organization demands solidarity. Lactic acid may retard the growth of intestinal flora and the up-keep of the intestinal toilet by larvage. Intoxication of some kind is a factor in many of the changes accompanying senility. Lorand thought age was chiefly due to atrophy and degenerative tissue by failure of the function of the ductless glands, especially the thyroid. The myxedematous look and are old. Thus the limit of life is a matter of excretion. The special organs of elimination cannot act to their full capacity or to that of vital necessity because of the replacement in senility of parenchyma by fibrous or fatty tissue. The retained waste products increase the sclerotic changes and produce a vicious circle--irritation, intoxication, and atheroma. The degeneration of the first stage produces insufficiency of the organs of elimination and the degeneration of all organs. As to physical manifestations, there is atrophy of the higher and more specialized cells and they are replaced by hypertrophied connective tissue. The heart is enlarged but this is compensatory for the stiffening and narrowing of the lumen of the great vessels near it and so the blood pressure is increased. The changes in bone, ligament, and tendons are extreme, with increased enervation throughout the body and perhaps senile marasmus, which may bring extreme emaciation or osteomalacia and even bone deformity. This may affect nervous and mental elements, like senile asystole and changes in the blood. The temperature, however, is not affected.