#Secondary Hæmorrhage.#--The term secondary hæmorrhage refers to bleeding that is delayed in its onset and is due to pyogenic infection of the tissues around an artery. The septic process causes softening and erosion of the wall of the artery so that it gives way under the pressure of the contained blood. The leakage may occur in drops, or as a rush of blood, according to the extent of the erosion, the size of the artery concerned, and the relations of the erosion to the surrounding tissues. When met with as a complication of a wound there is an interval--usually a week to ten days--between the receipt of the wound and the first hæmorrhage, this time being required for the extension of the septic process to the wall of the artery and the consequent erosion of its coats. When secondary hæmorrhage occurs apart from a wound, there is a similar septic process attacking the wall of the artery from the outside; for example in sloughing sore-throat, the separation of a slough may implicate the wall of an artery and be followed by serious and it may be fatal hæmorrhage. The mechanical pressure of a fragment of bone or of a rubber drainage tube upon the vessel may aid the septic process in causing erosion of the artery. In pre-Listerian days, the silk ligature around the artery likewise favoured the changes that lead to secondary hæmorrhage, and the interesting observation was often made, that when the collateral circulation was well established, the leakage occurred on the _distal_ side of the ligature. While it may happen that the initial hæmorrhage is rapidly fatal, as for example when the external carotid or one of its branches suddenly gives way, it is quite common to have one, two or more _warning hæmorrhages_ before the leakage on a large scale, which is rapidly fatal. The _appearances of the wound_ in cases complicated by secondary hæmorrhage are only characteristic in so far that while obviously infected, there is an absence of all reaction; instead of frankly suppurating, there is little or no discharge and the surrounding cellular tissue and the limb beyond are œdematous and pit on pressure. The _general symptoms_ of septic poisoning in cases of secondary hæmorrhage vary widely in severity: they may be so slight that the general health is scarcely affected and the convalescence from an operation, for example, may be apparently normal except that the wound does not heal satisfactorily. For example, a patient may be recovering from an operation such as the removal of an epithelioma of the mouth, pharynx or larynx and the associated lymph glands in the neck, and be able to be up and going about his room, when, suddenly, without warning and without obvious cause, a rush of blood occurs from the mouth or the incompletely healed wound in the neck, causing death within a few minutes.