This nerve appears in the furrow between the olivary body and the anterior pyramid, on a line with the anterior roots of the spinal nerves. It corresponds with the anterior roots in function, being a purely motor nerve. It bears impulses to the muscles of the tongue, and others attached to the hyoid bone.

Some sensory fibres lie in its descending branch, but these are probably derived from the vagus or trifacial nerves, with which its branches inosculate.

It is also said to contain the vasomotor fibres of the tongue.

Section of the nerves causes paralysis of the muscles of the tongue; when this is unilateral, the tongue inclines to the injured side, while being protruded from the mouth; but, while being drawn in, it passes to. the sound side. This is easily understood when it is borne in mind that the two acts depend upon the intrinsic muscles of the tongue, bringing about an elongation or shortening of the organ respectively.