The spinal cord shows an increased number of amyloid bodies, some diffuse sclerosis, often obliteration, by epithelial proliferation, of the central canal, and atrophy with pigmentation of the nerve cells, especially in the anterior cornua. The membranes may contain small calcareous plaques.

The arcus senilis, due to infiltration with fats, especially cholesterol and lipochrome, and to degeneration of elastic tissue at the periphery of the cornea, is often associated with arteriosclerosis (Monauni[148]). It is not a necessary accompaniment of age; among 321 persons over 80 years of age, it was absent in 114, or 35·5 per cent (Humphry); and it is well known that like grey hair, it may occur in those young in years. Nascher,[149] the author of Geriatrics, had an arcus senilis as a schoolboy. Rigidity and flattening of the crystalline lens lead to presbyopia, which may be premature and due to toxaemia, among the causes of which Ernest Clarke[150] gives intestinal toxaemia a high place. The power of accommodation is also impaired by weakness of the ciliary muscle brought about in the same way.

Skeleton.—The atrophy characteristic of senescence is well shown in the fixed tissues of the bony skeleton. Though the bones do not as a rule alter materially in size or shape, they do so markedly in substance from rarefaction and absorption, the latter taking place mainly from the inside of the bones and especially the cancellous tissue, the medullary cavity and the Haversian canals becoming larger (senile osteoporosis). Hence fractures near the joints, particularly intracapsular fracture of the neck of the femur, are favoured. The absorption of the alveolar border of the jaw is intimately connected with the loss of the teeth, and brings the mental foramen to the top of the edentulous mandible. The angle of the jaw at the junction of the body and the ramus now opens out and comes to resemble that of an infant. It is often stated that the angle of junction of the neck and shaft of the femur becomes less, more of a right angle, but Humphry regarded this as exceptional.

From muscular weakness the back becomes bent and as a result the vertebrae become altered in shape. Ossification of the anterior common spinous ligament—a change analogous to rheumatoid osteophytes around the more movable joints—is an added and not uncommon change but, like calcification of the costal and laryngeal cartilages, it is a morbid process, and when advanced constitutes spondylitis deformans. The intervertebral discs undergo some loss of elasticity and atrophy, thus contributing to the loss of height. The cranial bones are usually thinned, and the parietal bones may show symmetrical or nearly symmetrical oval areas of excessive absorption of the outer and even of the inner table, so that the epicranium and the dura mater may be in contact. These areas which are close to the longitudinal fissure must not in the case of ancient skulls be mistaken for examples of early trephining. The bony sutures tend to become obliterated. Instead of thinning and loss of weight the skull, especially the vault, may show thickening and be heavier than normal—a change involving chiefly the inner surface and ascribed by Sir George Humphry to shrinkage of the brain.

Calcification of the costal and laryngeal cartilages, which have a yellow tint from fatty change, is, like a similar change in the arteries, pathological and not part of the process of senescence. Thus among 10 recorded necropsies on centenarians the costal cartilages were calcified in 2 only. Calcification of the costal cartilages interferes with the respiratory movements and was regarded by Sir George Humphry, who tested for it by estimating the elasticity perceived when gentle pressure is exerted on the lower part of the sternum, as a bad omen for the future.

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.

The voluntary muscles, according to Durante,[156] contain many fibres with large globules of fat; but Jewesbury and Topley,[157] who describe coarse fat globules mingled with brown pigment in the immediate neighbourhood of the muscle nuclei in 50 per cent of cases of various kinds, and almost constantly in old subjects, regard this condition as independent of true fatty degeneration, and are doubtful if it has any pathological significance. Excessive fatty and fibrotic change is found in cases of senile paraplegia without any lesion in the spinal cord or brain.