Muscle Response to Foreign Innervation

Abstract

Whether a muscle with foreign innervation will respond by contraction to any impulse reaching it or only to specific impulses which are characteristic for that muscle, has not yet been finally determined. To study the behavior of muscles with foreign innervation, anastomoses have been made between the individual nerve trunks of the brachial and lumbar plexuses in albino rats. The following anastomoses have been successfully obtained: sciatic to median and ulnar, sciatic to the radial, median and ulnar to the femoral, and the median with the ulnar to the sciatic.

The cut ends of the nerves were approximated and held in place by suturing with silk to the body wall. While so held the outgrowing fibers of the regenerating proximal nerve trunk grew along the distal trunk to the new muscle groups. A high percentage of the proximal nerve trunks showed evidence of regeneration and in about 50% of the 60 animals operated upon the nerves reached the muscle groups toward which they were directed.

By frequently reopening the incisions in the skin it was possible to locate the growing nerves and to follow the rate of regeneration of the outgrowing fibers. In young rats about 100 gm. in weight the daily outgrowth was about 3 mm. These nerves reached the muscle groups in about 40 to 45 days after the operation. The final length of the regenerated nerves was generally more than 3 times their original length. Observations made with and without ligature of the terminal stumps showed no cases which could be interpreted as a union by first intention, i. e., Forsmann's suture.

The behavior of the muscle groups to which the foreign regenerating nerves were guided was studied by stimulating them electrically.