Experimental histological evidence for a dual motor pathway from the hypoglossal nucleus to lingual muscles in the guinea pig.

By combining the results of retrograde cell labelling with those of anterograde degeneration after nerve sectioning, it was shown that some axons from the most caudal neurones of the hypoglossal nucleus emerge in the first cervical nerve and join the hypoglossal nerve in the neck. These indirect hypoglossal axons are distributed to the intrinsic muscles of the tongue. The observed collaboration between the hypoglossal and first cervical nerves in supplying the lingual muscles has a plausible basis of explanation in phylogeny.