Bioengineering-blueprint for progress.

1 Acting Director, Prosthetic and Sensory Aids Service, U.S. Veterans Administration, Washington 25, D.C. THE limbs of m a n move in space and t ime, in response to systems of internal and external forces, and in accordance wi th the laws of mechanics. To restore to any satisfactory extent the functions lost through amputa t ion of an ext remi ty therefore requires in t imate knowledge not only of the s t ructure , form, and behavior of the normal l imb bu t also of the techniques available for producing complex motions in subst i tu te devices ac t ivated by residual sources of body power. Since adequate replacement of a na tu ra l limb with an artificial one requires successful integrat ion of the human mechanism with a toollike device, the biomechanical features of the s tump and the physical characteristics of the prosthesis mus t be wedded as nearly as possible into a single, functional ent i ty . Two-sided as this problem would now obviously appear , it is only in comparat ively recent years t h a t the medical sciences of surgery, ana tomy, and physiology and the physical one of engineering have been brought together in a unified a t t ack upon the whole problem of amputee rehabil i tat ion. Until recently, surgeons, with few exceptions, had little or no unders tanding of engineering problems. And heretofore the design and construction of artificial l imbs has been conducted most ly by art isans who, however ingenious they m a y have proved to be, were most ly wi thout formal education in engineering or ana tomy. Besides this, except in isolated instances the two worked separately and alone. All of which no doubt accounts for the fact tha t , as late as World W a r I I , the available artificial l imbs fell far short of the s tandards of accomplishment a t ta ined in other fields of research and invention. In the research program coordinated by the Advisory Commit tee on Artificial Limbs, Nat iona l Research Council, there have been brought together in harmonious working relationship the individual skills of surgeon and engineer in a sort of m u t u a l bioengineering to produce t ruly functional artificial limbs. As a result, there has been in the field of prosthet ics perhaps more progress during the pas t decade than in all the preceding 2000 years of limbmaking. Because the lower limb is more essential to h u m a n act ivi ty than is the arm,