To allow the pus to escape, it is necessary, under local anaesthesia, to cut away the nail fold as well as the portion of nail in the infected area, or, it may be, to remove the nail entirely.  If only a small opening is made in the nail it is apt to be blocked by granulations.

[Illustration:  FIG. 9.—­Diagram of various forms of Whitlow.
  a = Purulent blister.
  b = Suppuration at nail fold.
  c = Subcutaneous whitlow.
  d = Whitlow in sheath of flexor tendon (e). ]

Subcutaneous Whitlow.—­In this variety the infection manifests itself as a cellulitis of the pulp of the finger (Fig. 9, c), which sometimes spreads towards the palm of the hand.  The finger becomes red, swollen, and tense; there is severe throbbing pain, which is usually worst at night and prevents sleep, and the part is extremely tender on pressure.  When the palm is invaded there may be marked oedema of the back of the hand, the dense integument of the palm preventing the swelling from appearing on the front.  The pus may be under such tension that fluctuation cannot be detected.  The patient is usually able to flex the finger to a certain extent without increasing the pain—­a point which indicates that the tendon sheaths have not been invaded.  The suppurative process may, however, spread to the tendon sheaths, or even to the bone.  Sometimes the excessive tension and virulent toxins induce actual gangrene of the distal part, or even of the whole finger.  There is considerable constitutional disturbance, the temperature often reaching 101 or 102 F.

The treatment consists in applying a constriction band and making an incision over the centre of the most tender area, care being taken to avoid opening the tendon sheath lest the infection be conveyed to it.  Moist dressings should be employed while the suppuration lasts.  Carbolic fomentations, however, are to be avoided on account of the risk of inducing gangrene.

Whitlow of the Tendon Sheaths.—­In this form the main incidence of the infection is on the sheaths of the flexor tendons, but it is not always possible to determine whether it started there or spread thither from the subcutaneous cellular tissue (Fig. 9, d).  In some cases both connective tissue planes are involved.  The affected finger becomes red, painful, and swollen, the swelling spreading to the dorsum.  The involvement of the tendon sheath is usually indicated by the patient being unable to flex the finger, and by the pain being increased when he attempts to do so.  On account of the anatomical arrangement of the tendon sheaths, the process may spread into the forearm—­directly in the case of the thumb and little finger, and after invading the palm in the case of the other fingers—­and there give rise to a diffuse cellulitis which may result in sloughing of fasciae and tendons.  When the infection spreads into the common flexor sheath under the transverse carpal (anterior annular) ligament, it is not uncommon for the intercarpal and wrist joints to become implicated.  Impaired movement of tendons and joints is, therefore, a common sequel to this variety of whitlow.