(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].)
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.
The granulating surface to be covered in this manner must first be cleansed with a weak sublimate solution, followed by a sterilized normal salt solution. When an ulcerated or denuded surface requires skin-grafting, the best time to begin is as soon as there is evidence of the formation of new skin at the edges of the wound; in other words, when reparative action is becoming established. This does not apply to surfaces just denuded over healthy areas for plastic purposes, which should be grafted immediately.