macaques instead, which he considered structurally closest to man. Even though Galen was a qualified examiner, his research produced many errors owing to the limited anatomical material available to him. Vesalius contributed to the new Giunta edition of Galen's collected works and began to write his own anatomical text based on his own research. Until Vesalius pointed out Galen's substitution of animal for human anatomy, it had gone unnoticed and had long been the basis of studying human anatomy. Unlike Galen, Vesalius was able to procure a steady supply of human cadavers for dissection. In 1539, a judge at the Padua criminal court had been interested by Vesalius' work and had agreed to regularly supply him the cadavers of executed criminals. Galen had assumed that arteries carried the purest blood to higher organs such as the brain and lungs from the left ventricle of the heart, while veins carried blood to the lesser organs such as the stomach from the right ventricle. In order for this theory to be correct, some kind of opening was needed to interconnect the ventricles, and Galen claimed to have found them. So paramount was Galen's authority that for 1400 years a succession of anatomists had claimed to find these holes, until Vesalius admitted he could not find them. Nonetheless, he did not venture to dispute Galen on the distribution of blood, being unable to offer any other solution, and so supposed that it diffused through the unbroken partition between the ventricles. Other famous examples of Vesalius disproving Galen's assertions were his discoveries that the lower jaw (mandible) was composed of only one bone, not two (which Galen had assumed based on animal dissection) and that humans lack the rete mirabile, a network of blood vessels at the base of the brain that is found in sheep and other ungulates. In 1543, Vesalius conducted a public dissection of the body of Jakob Karrer von Gebweiler, a notorious felon from the city of Basel, Switzerland. He assembled and articulated the bones, finally donating the skeleton to the University of Basel. This preparation ("The Basel Skeleton") is Vesalius' only well-preserved skeletal preparation, and also the world's oldest surviving anatomical preparation. It is still displayed at the Anatomical Museum of the University of Basel. In the same year Vesalius took residence in Basel to help Johannes Oporinus publish the seven-volume De humani corporis fabrica (On the fabric of