_The teeth_ are usually, but not invariably, few in the aged, for care or lack of it, the accumulated effect of long-continued mechanical injuries, altered calcium metabolism, and diminished resistance to infection will necessarily influence the amount of decay. Statistics, especially Humphry’s, show that in extreme old age very few teeth are present, and it is tempting to correlate the diminished provision for mastication with the lessened need for food. Sir Isaac Newton, however, at the age of 85 was said to have lost one tooth only. The numerous reputed instances of a third dentition can be explained only by the appearance of a previously buried tooth through the atrophying gums, for a genuine third dentition would necessitate the presence of dental germs which do not exist. _The gastro-intestinal tract_ shows atrophy of the muscular coat and its secreting glands, so that dilatation of the thin-walled, pale stomach and colon occur on less provocation than in adult life and digestion is impaired; from lack of mucous secretion combined with loss of motor vigour constipation is common. It may be added that hypertrophy of the prostate by interfering with peristalsis of the colon has been thought to cause gerontal constipation (Hollis[151]). The pancreas shows fibrotic atrophy and becomes smaller and harder. From the loss of fat and muscular atrophy visceroptosis is not uncommon. _The liver_ diminishes in size and weight by about one half; atrophy of considerable areas may expose the vessels and ducts on the surface of the organ. Boyd’s tables show a difference of 18 oz. between the weights in persons in the decade 20–30 and in those over 80. Microscopically atrophy of the lobules and of the cells in the centres of the lobules have been described (Luciani[152]), but the latter change is not constant, for in a woman of 93 Salimbeni and Gery[153] definitely noted that the cells were not atrophied. That such atrophy of the liver cells is pathological is perhaps supported by D. Symmers’s[154] observation that in the pancreas of such cases the islands of Langerhans may show moderate enlargement, as if to compensate for failure of the glycogenic function of the liver. Pigmentation of the cells by a lipochrome is excessive, and the name brown atrophy has been applied to the condition which is seen in the other viscera of the old. _The lungs_ become smaller, lighter, and the elastic tissue degenerates; this is atrophous emphysema, and the chest capacity diminishes. Roussy and Leroux[155] found that these lungs commonly show endarteritis obliterans and fibrosis, conditions which favour infarction, infection, and the terminal bronchopneumonia to which the aged are so prone.