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 fasciæ 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.

The _treatment_ consists in inducing passive hyperæmia by Bier's method,
and, if this is done early, suppuration may be avoided. If pus forms,
small incisions are made, under local anæsthesia, to relieve the tension
in the sheath and to diminish the risk of the tendons sloughing. No form
of drain should be inserted. In the fingers the incisions should be made
in the middle line, and in the palm they should be made over the
metacarpal bones to avoid the digital vessels and nerves. If pus has
spread under the transverse carpal ligament, the incision must be made
above the wrist. Passive movements and massage must be commenced as
early as possible and be perseveringly employed to diminish the
formation of adhesions and resulting stiffness.

_Subperiosteal Whitlow._--This form is usually an extension of the
subcutaneous or of the thecal variety, but in some cases the