[Comparative-anatomical investigation of the M. extensor hallucis longus in man]

The authors have analysed the variations of the M. extensor hallucis longus in man from the standpoint of evolutionary myology. The variations of the muscle indicate that in modern man it has transformed itself in the medially as well as in the laterally direction. Consequently it forms 2 new muscles: M. extensor hallucis longus accessorius medialis and M. extensor hallucis longus accessorius lateralis. The reorganization in the medial direction is phylogenetically older than that in the lateral direction. Of all primates these 2 muscles appear only in man representing a new acquisition. The new additional muscles and their transitional forms can be found independently and also together in various combinations. The additional tendons and muscles widen the insertion of the M. extensor hallucis longus medially and laterally. The authors emphasize that the reorganization in the medial direction is independent from that in the lateral direction.