Senescence has some nosological compensations; thus some acute infections, such as measles, scarlet fever, enteric fever, and diphtheria, are very rare, probably because immunity has gradually been developed in the course of time; pneumonia and erysipelas, however, are notable exceptions in being specially prone to occur in the aged. Migraine usually becomes less troublesome or disappears with the march of years. As mentioned on p. 86, malignant disease is comparatively rare in very advanced age; lymphadenoma and leukaemia are rarer than in early life; and as pathological, like normal, processes are slower, carcinoma, especially of the breast, may become stationary. _Diseases of the Skin._--From atrophy of the skin and its secretory glands the skin is less resistant to infection and accordingly has been thought to be more susceptible to parasitic attack, such as pityriasis versicolor. The aged who are often less scrupulous in cleanliness than their juniors are more prone to skin affections, such as eczema, erythema, and erysipelas. The so-called senile prurigo is largely due to the presence of lice. From the atrophic condition of the skin the cutaneous nerves are more exposed, and this has been regarded as playing a causal part in senile pruritus, which is an exception to the general rule that sensory impressions are less prominent in the aged than earlier in life. It may, like prurigo, be due to an external cause, such as pediculi, or it may be metabolic in origin. In almshouses and institutions for the aged epidemics of scratching may develop from imitation of a genuine case of pruritus. Senile pruritus is usually general and from its obstinate resistance to treatment may be a terrible affliction. Sir Gilbert Blane (1749–1834) suffered from it for the last 13 years of his life, and was obliged to take opium in increasing quantities until his daily dose reached the equivalent of a dram of the solid drug. Erysipelas, like pneumonia, with which or with bronchopneumonia it may be combined, is less obvious in its symptoms than in ordinary adult life on account of the diminished power of reaction, as shown by the slight degree of leucocytosis in the aged in erysipelas (Lamy) and by its longer course. From want of resistance and arteriosclerosis, especially Mönckeberg’s form with calcification of the media, senile gangrene may follow slight accident or injury, such as occurs in cutting the toe nails. Absorption from the gangrenous area may cause toxic glycosuria, and such cases, when they come under observation at this stage, are sometimes regarded as diabetic gangrene. It is remarkable how well amputations for diabetic gangrene do; in July 1922 I saw with Professor F. H. Edgeworth a man with double amputation of the legs perfectly healed, and in good health though the glycosuria persisted.