_Burns of Third Degree--Partial Destruction of the Skin._--The epidermis and papillæ are destroyed in patches, leaving hard, dry, and insensitive sloughs of a yellow or black colour. The pain in these burns is intense, but passes off during the first or second day, to return again, however, when, about the end of a week, the sloughs separate and expose the nerve filaments of the underlying skin. Granulations spring up to fill the gap, and are rapidly covered by epithelium, derived partly from the margins and partly from the remains of skin glands which have not been completely destroyed. These latter appear on the surface of the granulations as small bluish islets which gradually increase in size, become of a greyish-white colour, and ultimately blend with one another and with the edges. The resulting cicatrix may be slightly depressed, but otherwise exhibits little tendency to contract and cause deformity. _Burns of Fourth Degree--Total Destruction of the Skin._--These follow the more prolonged action of any form of intense heat. Large, black, dry eschars are formed, surrounded by a zone of intense congestion. Pain is less severe, and is referred to the parts that have been burned to a less degree. Infection is liable to occur and to lead to wide destruction of the surrounding skin. The amount of granulation tissue necessary to fill the gap is therefore great; and as the epithelial covering can only be derived from the margins--the skin glands being completely destroyed--the healing process is slow. The resulting scars are irregular, deep and puckered, and show a great tendency to contract. Keloid frequently develops in such cicatrices. When situated in the region of the face, neck, or flexures of joints, much deformity and impairment of function may result (Fig. 63). [Illustration: FIG. 63.--Cicatricial Contraction following Severe Burn.] In _burns of the fifth degree_ the lesion extends through the subcutaneous tissue and involves the muscles; while in those of the _sixth degree_ it passes still more deeply and implicates the bones. These burns are comparatively limited in area, as they are usually produced by prolonged contact with hot metal or caustics. Burns of the fifth and sixth degrees are met with in epileptics or intoxicated persons who fall into the fire. Large blood vessels, nerve-trunks, joints, or serous cavities may be implicated. #General Phenomena.#--It is customary to divide the clinical history of a severe burn into three periods; but it is to be observed that the features characteristic of the periods have been greatly modified since burns have been treated on the same lines as other wounds.