An attempt to reproduce tendon sheaths using autologous venous grafts has been undertaken in Cercopithecus aethiops (Blue Vervet Monkey). Ten venous grafts were tested. Five were placed around sutured tendons in paratenon, and the remainder around tendons in sheath formation. In no instance did synovial-like sheaths form. In the latter series, the experiment was controlled, and the results obtained expressed in terms of function. The functional results of the venous ensheathed tendons were worse than those of the controlled tendons.The controlled experiment was confined to the digital sheath, an area notoriously liable to adhesion formation, and the one which offered the most critical test of operative technique.A method for the evaluation of function, following the repair of divided tendons in the experimental animal has been presented. Voluntary movement of joints in the experimental animal was obviously impossible, but the method employed in this experiment, namely, the electrical stimulation of muscles, and the photographic recording of the range of joint movement, presented no disadvantages.The experimental animal used in this study was ideal, in that anatomical studies of the hand of this species, revealed features both structurally and functionally comparable to those in man.The anatomical and physiological aspects of tendon action, the mechanics of tendon gliding, and the healing processes in divided tendons have been studied.The fate of human autologous venous grafts has been investigated.A review of previous methods employed to prevent peritendinous adhesions has been presented.