In this inflammation, which constitutes chilblains, the sides of the small blood-vessels become paralyzed, and losing their contractility, are dilated by the pressure of the blood within them. If the inflammation be not abated, that is to say, if the little blood-vessels are not restored to their original size, and to their natural contractility, they burst, and matter will be formed, or mortification may ensue. This contractility depends upon proper nervous action in those small fibres which give life to the sides of the hair-like vessels, or small blood-pipes. Any sudden shock of cold or heat deprives these nerves of their power, and induces a local paralysis. The change from cold to heat oftener produces this shock than that from heat to cold; but either sudden alternation will produce chilblain. It need hardly be said that the nerves of persons in low states of health, persons of scrofulous habits, and young persons in whom the tissues are delicate, are more liable to be locally paralyzed in the manner described, than those persons of robust constitution, having a large quantity of vitality to resist such attacks. Hence we find such invalids, scrofulous persons, and children, more liable to chilblain than others. The liability to chilblain is often an indication of a low state of health, and want of healthy vital action in the system. When the nature of chilblains is understood, the mode of prevention will be at once perceived, viz.—1st. To protect the parts most liable to the attack (hands and feet) from sudden alternations, either from cold to heat, or from heat to cold. 2dly. To keep the constitution in such a healthy state as to make all parts possess such vitality as to be able to resist slight alternations in temperature.