Unusual as the opportunities are for reconstruction work on the upper extremity, they are counterbalanced by an adequate amount of technical difficulties. To overcome these, investigation into numerous questions of a theoretical as well as a technical nature becomes necessary. Some detail work has been devoted to the solution of surgical problems; much less attention has been given to the study of the principles of a mechanical or a physiologic nature. Yet it would seem that mechanical and physiologic analysis is as essential for systematic progress in this field as it is in other fields of surgery. Conditions existing in the wrist and hand compare favorably with those of the foot and ankle for several reasons: The muscle supply is more abundant; there is, as shall be shown presently, a greater possibility of detaching muscles of the hand and forearm for the purpose of transplantation, by virtue of certain anatomic