When thoracic flaps are used they may be directly sewn at their free ends to the part to be covered, as, for instance, in the forearm or arm, or they are stitched to the forearm to be later transferred to another part of the body after their circulation had become established. The various methods of the employment of these bridging flaps will be taken up individually in their respective places farther on. V. TRANSPLANTATION OF NONPEDUNCULATED FLAPS OR SKIN-GRAFTING Where there is loss of skin due to injury or operative procedure the parts may heal by granulation, but as this requires much time, and the consequent cicatrice causes considerable deformity, the granulating or freshly made wounds are covered with so-called detached skin flaps or grafts, when the former methods of plastic surgery cannot be followed. The methods employed in skin-grafting may be classified as: 1, autodermic; 2, heterodermic; 3, zoödermic. 1. _Autodermic_, when the grafts are taken from the tissue of the patient. 2. _Heterodermic_, when the grafts for the patient are taken from other persons. 3. _Zoödermic_, when the grafts for the patient are taken from the lower species. The former two classes may for convenience be again subdivided into 1. (_a_) Auto-epidermic. (_b_) Autodermic. 2. (_c_) Hetero-epidermic. (_d_) Heterodermic. The third class will permit of a great many subdivisions, too numerous to mention, each taking its name from the source of the graft. _1. Autodermic Skin-grafting_ =a. Auto-epidermic Skin-grafting.=—The method of covering granulation areas with small circular pieces of detached skin, pin grafts, was first advocated by J. Reverdin in 1870. The Reverdin method is applicable to healthy granulating surfaces only. The small lentil-form skin grafts are obtained from the arm or other suitable part of the body by raising the superficial layer of the skin with a tenaculum hook and cutting the conelike elevation off with delicate scissors. The grafts thus obtained contain the epiderm and corium and a slight base of the Malpighian layer. They are immediately transferred, without handling, to the granulating surface and fixed by the gentle pressure of the hook point. The skin may be transfixed with an ordinary sewing needle and the graft cut away with a delicate flat knife or razor blade, or scissors especially designed for the purpose may be used. (See Fig. 84.) [Illustration: FIG. 84.—SMITH SKIN GRAFTING SCISSORS.] A number of these grafts are often needed to cover a defect, in which case they are placed side by side upon the surface with a little space between their borders. Several such operations may be necessary, as many of the grafts are liable to die from malnutrition, pressure, or defective cutting.