If it is not let out by incision, the pus, travelling along the lines of least resistance, tends to point at several places on the surface, or to open into joints or other cavities.

Prognosis.—­The occurrence of septicaemia is the most serious risk, and it is in cases of diffuse suppurative cellulitis that this form of blood-poisoning assumes its most aggravated forms.  The toxins of the streptococci are exceedingly virulent, and induce local death of tissue so rapidly that the protective emigration of leucocytes fails to take place.  In some cases the passage of masses of free cocci in the lymphatics, or of infective emboli in the blood vessels, leads to the formation of pyogenic abscesses in vital organs, such as the brain, lungs, liver, kidneys, or other viscera. Haemorrhage from erosion of arterial or venous trunks may take place and endanger life.

Treatment.—­The treatment of diffuse cellulitis depends to a large extent on the situation and extent of the affected area, and on the stage of the process.

In the limbs, for example, where the application of a constricting band is practicable, Bier’s method of inducing passive hyperaemia yields excellent results.  If pus is formed, one or more small incisions are made and a light moist dressing placed over the wounds to absorb the discharge, but no drain is inserted.  The whole of the inflamed area should be covered with gauze wrung out of a 1 in 10 solution of ichthyol in glycerine.  The dressing is changed as often as necessary, and in the intervals when the band is off, gentle active and passive movements should be carried out to prevent the formation of adhesions.  After incisions have been made, we have found the immersion of the limb, for a few hours at a time, in a water-bath containing warm boracic lotion or eusol a useful adjuvant to the passive hyperaemia.

Continuous irrigation of the part by a slow, steady stream of lotion, at the body temperature, such as eusol, or Dakin’s solution, or boracic acid, or frequent washing with peroxide of hydrogen, has been found of value.

A suitably arranged splint adds to the comfort of the patient; and the limb should be placed in the attitude which, in the event of stiffness resulting, will least interfere with its usefulness.  The elbow, for example, should be flexed to a little less than a right angle; at the wrist, the hand should be dorsiflexed and the fingers flexed slightly towards the palm.

Massage, passive movement, hot and cold douching, and other measures, may be necessary to get rid of the chronic oedema, adhesions of tendons, and stiffness of joints which sometimes remain.

In situations where a constricting band cannot be applied, for example, on the trunk or the neck, Klapp’s suction bells may be used, small incisions being made to admit of the escape of pus.

If these measures fail or are impracticable, it may be necessary to make one or more free incisions, and to insert drainage-tubes, portions of rubber dam, or iodoform worsted.