“When these matters are taken into account, many things at once present themselves in regard to the arterial system, which deserve careful consideration; especially the fact that there is hardly a single vein going to the stomach, the intestines, or even the spleen, without its accompanying artery, and that nearly every member of the portal system has a companion artery associated with it in its course. Again, the arteries going to the kidneys are of such size that they can by no means be affirmed to serve merely for regulating the heat of these organs; and still less can we assert that so many arteries are distributed to the stomach, intestines and spleen for that purpose alone. And there is, furthermore, the fact, which we must for many reasons admit, that there is through the arteries and veins a mutual flux and reflux of materials, and that within these vessels the weight and gravitation of their contents has no effect”. The Seventh Book. In the seventh book, consisting of less than sixty pages, Vesalius fully describes the anatomy of the brain, of the cranial nerves, and of the organs of sense. His description of the eye is not as near accuracy as might be expected. He places the crystalline lens in the centre of the globe. His description of the organ of vision was only slightly better than that which was given by Galen. Vesalius showed, however, that the optic nerve is not a hollow tube, and that it does not enter the eyeball exactly in the antero-posterior axis. Conclusion Considering the time in which he lived, Vesalius was remarkably free from errors. Although to him the arteries were carriers of vital spirits, the veins were the true blood vessels, and, according to the first edition of his great book, the septum of the heart was filled with foramina; yet, we must say with Baas, “these are all mere shadows necessary to the brilliancy of the picture”. Vesalius was more than an anatomist. As a practical physician he had the highest reputation among his contemporaries. He was an accomplished scholar and was thoroughly conversant with the weaknesses of human nature, as is evident from many satirical touches in his writings. Although his great work contains many errors that a tyro of the present day would laugh at, it laid the foundations of our knowledge. Vesalius overthrew the idol of authority in anatomy and taught us to look at Nature with our own eyes.