This section is from the book "Anatomy Of The Arteries Of The Human Body", by John Hatch Power. Also available from Amazon: Anatomy of the Arteries of the Human Body, with the Descriptive Anatomy of the Heart.
Some of the irregularities in the origin of this vessel have been already described : in addition it may be remarked, that it has been seen to take its origin from the descending aorta. When it does not arise from the arch at the usual place, it must necessarily vary in its course. Velpeau mentions a curious irregularity of this vessel:—" After its origin, it passed to the left, in order to turn over the trachea, then penetrated between this organ and the oesophagus, and replaced itself on the right side at the moment of its bifurcation, but much more deeply than in the natural state."*
In some cases its length is less, and in others greater than what we have described. Guthrie states that in ordinary cases the artery is two inches and a half in length.
The Middle Thyroid of Neubauer, when present, usually arises from this vessel: the inferior thyroid also may arise from it.