The effect of position on the migration of muscle.

The tibial insertion of the M. semitendinosus of young rabbits was moved to a new location on the shaft of the tibia, either 5 or 10 mm proximal, or 0, 10, 20, 30, 40, or 50 mm distal to its original position. The animals were killed 8.5 months later. The results show that the greatest amount of proximal migration of the experimental muscles was 11.3 mm and this occurred in the muscles moved 10 mm distally. This compared with a migration of 12.8 mm for control muscles. The amount of proximal migration decreased progressively when the insertion was moved more or less than 10 mm distally. There was a small amount of distal migration in the 10 mm proximal, and the 40 and 50 mm distal groups. These results confirm experiments reported earlier in which muscles were not moved more than 20 mm distally. They support the hypothesis that migration is controlled by the position on the growing bone rather than by the tension in the muscle.