1. In some cases of ossification of the tendo achillis, the ossification arises from the calcaneum and is of periosteal origin. In other cases, the bone arises in the midst of the tendon. In spite of a great deal of experimental work and many clinical observations, the exact mechanism of this ossification is not clear.
2. The possibility that in some cases this condition is due to congenital defect should still be considered. Four of the cases reported showed a congenital talipes. The case which the author has reported showed a congenital defect in the neural arch of the first sacral segment.