The winter whitening of mammals is, therefore, precisely similar to the senile bleaching of human hair, no shift of the coat taking place.
This physiological wasting is termed senile atrophy.
These changes are found in senile wasting, in metaplasia of cartilage, in many tumours, especially mixed growths of the parotid gland and testicle, and in various inflammatory granulation ulcers.
Moreover, the last stages of individual life are prophetic not only of future rising and progressing derivatives, but in the case of senile individuals of future declining and degradational series.
Such injuries are apt to occur in syphilitic endarteritis, or senile arterial decay, whereby an artery may be blocked permanently, as if with an embolus, and the area supplied by it, in so far as it was dependent upon this vessel, deprived of nutrition.