(i) When the epidermis is merely scorched and reddened, but not separated from the true skin.
(ii) When the epidermis is raised, forming blisters.
(iii) When the true skin is involved, but not completely destroyed.
(iv) When the true skin is completely destroyed. In this and in the two following degrees the question of the contraction of scar tissue on healing becomes one of much importance.
(v) Where the muscles, etc., are involved.
(vi) Where the whole limb is implicated down to the bone.
The symptoms of a severe burn are grouped under three stages. The first is the stage of collapse with low temperature and feeble pulse; then, after about two days, comes the stage of reaction, with inflammatory fever. Pleurisy or peritonitis may now declare themselves, and the burnt surface undergoes suppuration and smells offensively. The third stage is that of exhaustion.
A curious and unexplained sequel of burns is ulceration of the intestinal mucous membrane, and particularly of the duodenum.