The venous blood of the neck region in mule is returned to the heart through the V. jugularis externa, V. vertebralis and V. cervicalis profunda. An internal jugular vein was not demonestrated in any specimen as the case in horse.
The V. vertebralis emerges from the transverse foramen of the 3rd cervical vertebra, crosses the joint capsule between the 3rd and 2nd cervical vertebrae. It reaches the atlantic fossa where it joins the R. anastomoticus cum. V. occipitalis. It detaches a stem vessel for R. descendens and V. emissaria foraminis occipitalis and enters the lateral vertebral foramen of the atlas to join the ventral internal vertebral vertebral venous plexus.