Nerve supply to the accessory soleus muscle

An accessory soleus muscle was found in the right leg of a cadaver in the dissecting room. This anomalous muscle was situated medially between the distal part of the tibia and the tendo calcaneus. The muscle arose from the anterior aponeurosis of the soleus muscle and was attached with a separate tendon to the calcaneus anteromedial to the tendo calcaneus. The soleus muscle was supplied by two nerves from the tibial nerve. The ramus posterior entered its posterior surface near the proximal border, and the ramus anterior entered the bipenniform part which was located on the anterior aspect of the soleus. One of branches from the r. anterior descended on the surface of the medial half of the bipenniform part and gave off a few twigs for this muscle part. Finally, its terminal entered the accessory soleus muscle and ramified in this muscle. In a teased preparation of the tibial nerve, both the nerve fibres composing this branch to the anomalous muscle and those constituting the r. anterior proper which supplied the bipenniform part were contained in the same funiculus. This mode of nerve supply to the soleus and the accessory soleus muscle suggested that this anomalous muscle derived from the part of the proper soleus muscle supplied by the r. anterior.