+Effects of Cold.+ The more serious effects consequent upon exposure to sudden or prolonged cold are termed _frost bite_. In this condition the feet are commonly affected, and very often the freezing is so complete that upon thawing, the parts are found to be absolutely dead or their vitality so impaired by the cold that after reaction, strangulation and inflammation of the tissues occur, producing gangrene. As in burns there are three degrees of freezing, viz., first, second and third. In the first, the redness, numbness and tingling which follow exposure to intense cold are succeeded by loss of power, usually commencing in the toes, and loss of sensation, the parts becoming anemic and cold. In the second degree the skin is red or bluish and is covered by blebs with clear hemorrhagic contents. If the epidermis only is lifted up there is quick, scarless healing, but in the majority of cases the deeper tissues are involved. In frost bites of the third degree there are blebs and crusts which eventually mortify. Parts hopelessly frozen are at first anemic, cold and insensible but after reaction sets in they become swollen and discolored or they shrivel up and contract. It is not unusual for the part to show no change for some days and then to become blue or black; a line of demarcation forms and the dead tissue sloughs off. +Treatment.+ Reaction must be gradual. The room should be of low temperature; the affected part should be immersed in ice water; gentle friction or rubbing lightly with snow is oftimes efficacious. When the temperature is normal, stimulating friction with soap liniment, alcohol, and water and spirits of camphor with elevation of the parts, is advisable. The room may be gradually warmed and the parts exposed should then be covered with cotton. As reaction progresses warm, stimulant drinks may be cautiously administered. If excessive reaction takes place, evaporating lotions of alcohol and water may be used. Where a large surface is frozen, prolonged immersion in a bath may be employed after reaction has been established. When gangrene is present, surgical intervention is imperative. +Chilblain+ occurs in individuals with a feeble circulation or in the anemic or strumous, though healthy young people are not immune. The feet are very often attacked, especially the heel and the borders of the feet, but any of the peripheral parts may be affected. The areas are bluish or purplish red, swollen, cold to the touch, tender, itching and burning. Neglect and friction will produce severer grades of inflammation, with vesicles, bullae, pustules and ulceration or even gangrene, with or without the formation of bullae. There may be a favorable termination or fatal septicema may supervene.