1. This study has confirmed an earlier report that canine flexor digitorum profundus tendons divided and repaired within the flexor digital sheath are healed by the cellular activity of the sheath and surrounding tissues and not by any intrinsic tenoblastic proliferation.
2. Blocking tubes placed about sites of tendon repair require the healing cellular and vascular elements of the sheath to grow beneath the tubing to reach wound sites. Healing of tendons is thereby delayed or prevented, or both, entirely and is often preceded by tendon degeneration.
3. When tendon healing does occur within blocking tubes of polyethylene and millipore, it is often through the medium of a dense, granular, ungliding vascular sear which is slow to mature. In all events, gross and histological observations reveal two sets of thick adhesions at tube ends rather than the mild filmy adhesions at the wound sites normally expected if no tubing is used.