The technique for cutis-grafting must be without a flaw, and the asepsis absolute; there must not only be a complete absence of movement, but there must be no traction on the flap that will endanger its blood supply.

Owing to the uncertainty in the results of cutis-grafting the two-stage or indirect method has been introduced, and its almost uniform success has led to its sphere of application being widely extended.  The flap is raised as in the direct method but is left attached at one of its margins for a period ranging from 14 to 21 days until its blood supply from its new bed is assured; the detachment is then made complete.  The blood supply of the proposed flap may influence its selection and the way in which it is fashioned; for example, a flap cut from the side of the head to fill a defect in the cheek, having in its margin of attachment or pedicle the superficial temporal artery, is more likely to take than a flap cut with its base above.

Another modification is to raise the flap but leave it connected at both ends like the piers of a bridge; this method is well suited to defects of skin on the dorsum of the fingers, hand and forearm, the bridge of skin is raised from the abdominal wall and the hand is passed beneath it and securely fixed in position; after an interval of 14 to 21 days, when the flap is assured of its blood supply, the piers of the bridge are divided (Fig. 1).  With undermining it is usually easy to bring the edges of the gap in the abdominal wall together, even in children; the skin flap on the dorsum of the hand appears rather thick and prominent—­almost like the pad of a boxing-glove—­for some time, but the restoration of function in the capacity to flex the fingers is gratifying in the extreme.

[Illustration:  FIG. 1.—­Ulcer of back of Hand covered by flap of skin raised from anterior abdominal wall.  The lateral edges of the flap are divided after the graft has adhered.]

The indirect element of this method of skin-grafting may be carried still further by transferring the flap of skin first to one part of the body and then, after it has taken, transferring it to a third part.  Gillies has especially developed this method in the remedying of deformities of the face caused by gunshot wounds and by petrol burns in air-men.  A rectangular flap of skin is marked out in the neck and chest, the lateral margins of the flap are raised sufficiently to enable them to be brought together so as to form a tube of skin:  after the circulation has been restored, the lower end of the tube is detached and is brought up to the lip or cheek, or eyelid, where it is wanted; when this end has derived its new blood supply, the other end is detached from the neck and brought up to where it is wanted.  In this way, skin from the chest may be brought up to form a new forehead and eyelids.

Grafts of mucous membrane are used to cover defects in the lip, cheek, and conjunctiva.  The technique is similar to that employed in skin-grafting; the sources of mucous membrane are limited and the element of septic infection cannot always be excluded.