Non-recovery leads ultimately to gangrene. If superficial, the part may separate of itself, leaving a good new skin underneath which is at first very tender; if deeper, judicious amputation may be required. The gangrene may be _dry_ or _moist_. In the former case the part shrinks and becomes black and scaly, the condition having little effect upon the general health. It is dry and inoffensive. In the case of moist gangrene the part becomes septic, is very offensive, and absorption of poisons leads to impaired health. The amount of the limb that requires amputation depends upon the severity and extent of the frost-bite. It must be emphasized that in examining a part for frost-bite the waxy appearance may not be present. It does not follow that the part has not been frost-bitten or is not seriously affected. There is a more slowly produced condition, due to the action of prolonged cold, in which blood returning into the capillaries which have been damaged by the continued constriction due to the cold sets up inflammation and exudation, which may lead to death of the part. Signs of mottling, at first pinky white, later blue-grey, should be looked for, and if they appear the parts must be treated with the greatest care. If circumstances permit, the limb should be raised, rested, and dry, warm (not hot) dressings applied. For unbroken parts I use cotton wool which has been thoroughly dried, bandaged lightly; for cases when the skin is broken, lint which has been warmed and the surface scorched to render it sterile, covered with warm, dry wool, and again lightly bandaged. This simple treatment can be applied under any conditions in which it is possible to produce a flame. Cases take a long time to recover fully. Ointments, hot wet dressings, and poultices should be avoided. A milder though similarly produced effect leads to an irritable condition resembling chilblains. It affects commonly the tips of the ears. The momentary exposure of bare skin does not lead to immediate frost-bite, but the length of time that it can be exposed depends upon the temperature, the amount of moisture present, and the strength of wind. It is often necessary in carrying out a piece of work to expose the hands, which may require periodical warming up. Much depends upon the circulation, for if a job is attempted after the body has been for some time at rest frost-bite sets in quickly. If, on the other hand, the individual has been working hard, walking or running, and the blood is pulsating actively, the hands and other parts can be exposed for comparatively long periods without harm. As a result of unrecognized and untreated frost-bite strong men have been crippled for life. Constant watchfulness is required; its danger cannot be over-estimated, nor too much emphasis placed upon measures for its prevention. _Notes on Oils and Grease_