#Reactionary Haemorrhage.#—­Reactionary or intermediary haemorrhage is really a recurrence of primary bleeding.  As the name indicates, it occurs during the period of reaction—­that is, within the first twelve hours after an operation or injury.  It may be due to the increase in the blood-pressure that accompanies reaction displacing clots which have formed in the vessels, or causing vessels to bleed which did not bleed during the operation; to the slipping of a ligature; or to the giving way of a grossly damaged portion of the vessel wall.  In the scrotum, the relaxation of the dartos during the first few hours after operation occasionally leads to reactionary haemorrhage.

As a rule, reactionary haemorrhage takes place from small vessels as a result of the displacement of occluding clots, and in many cases the haemorrhage stops when the bandages and soaked dressings are removed.  If not, it is usually sufficient to remove the clots and apply firm pressure, and in the case of a limb to elevate it.  Should the haemorrhage recur, the wound must be reopened, and ligatures applied to the bleeding vessels.  Douching the wound with hot sterilised water (about 110 F.), and plugging it tightly with gauze, are often successful in arresting capillary oozing.  When the bleeding is more copious, it is usually due to a ligature having slipped from a large vessel such as the external jugular vein after operations in the neck, and the wound must be opened up and the vessel again secured.  The internal administration of heroin or morphin, by keeping the patient quiet, may prove useful in preventing the recurrence of haemorrhage.

#Secondary Haemorrhage.#—­The term secondary haemorrhage 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 haemorrhage, 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 haemorrhage 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 haemorrhage.  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