Part 8

The Fabrica is built upon a practical plan. It treats of anatomy in a logical manner and is composed of seven books, which deal with the following subjects: (1)—Bones and Cartilages; (2)—Ligaments and Muscles; (3)—Veins and Arteries; (4)—Nerves; (5)—Organs of Nutrition and Generation; (6)—Heart and Lungs; and (7)—Brain and Organs of Sense.

The First Book

Vesalius devotes one hundred and sixty-eight pages to the bones and cartilages, treating these structures with a thoroughness that amazed his contemporaries. He was the first author who correctly described the osseous system as a whole. In numerous instances Vesalius places himself in direct opposition to the opinions of Galen. He denied the existence of the intermaxillary bone in adults, and showed that the inferior maxilla does not consist of two pieces, as has been asserted by Galen. The seven bones of the sternum were reduced to three by Vesalius. He denied Galen’s statement that the bones of the symphysis pubis separate during parturition. He was the first anatomist to give an accurate description of the sphenoid bone. A small aperture at the root of the pterygoid process of the sphenoid bone is called foramen Vesalii. Vesalius proved the existence of marrow in the bones of the hand, which had been denied by Galen. In all respects, he wrote more intelligently of the bones than any anatomist who had preceded him.

The Second Book

Vesalius devotes one hundred and eighty-eight pages to a description of the ligaments and the muscles. This part of his treatise, while it contains a few errors and does not reach the high plane of the first book, is superior to any work of its kind that had preceded it. Vesalius was the first writer to describe the internal pterygoid muscle. He denied the existence of a general muscle of the skin, and stated that the intercostal muscles merely separate the ribs without expanding or contracting the thorax. He held the view that nerves and muscles do not stand in any relation of proportionate strength to one another, large nerves often being distributed to small muscles. He also held that the tendons are similar in structure to the ligaments.

Vesalius’s plates of the superficial muscles are among the most beautiful that have ever appeared. They have been copied in practically all later treatises on anatomy, and have been used extensively by art-anatomists. His plates of the deeper muscles, while naturally not so pleasing to the eye, are wonderfully near accuracy. The different muscles are drawn to show function as well as structure.

The Third Book

The third part of the Fabrica, comprising sixty pages, is devoted to the veins and arteries. Vesalius begins with the definition of a vein, and describes the structure of these vessels in general. The term “artery” is treated in like manner. He introduces several small illustrations which serve to elucidate this part of the text. His first large plate in this section is devoted to the venae portae. This is followed by a full-page picture of the entire venous system. The arterial system is fully described and elaborately illustrated. To these is added another plate, in which both arteries and veins are represented in their natural order. In other plates he shows the special circulations—cerebral, portal, and pulmonary.

Vesalius described the valve which guards the foramen ovale in the foetus, and also noticed the valve-like fold which guards the entrance of each hepatic vein into the inferior vena cava. He also gave an admirable description of the vena azygos. Blinded by the ancient theory of the movement of the blood—a sort of flux and reflux in the veins, he overlooked the function of the venous valves. He described them as eminences, or projections, or accidental rugosities, which in no way interfere with the flux and reflux of the blood.

The Fourth Book

Vesalius devotes forty pages to the cerebral and spinal nerves. The anatomy of the brain is treated in the seventh book. His representations of the nerves are very creditable. He mentions eleven pairs of cranial nerves: the olfactory, the optic, the motores oculorum, the trifacial, the abducens, the portio dura, the portio mollis, the glosso-pharyngeal, the pneumogastric, and the spinal accessory.

His account of the brain—contained in the seventh book—is elaborately minute considering the time when it was written. His illustrations and description of this organ surpass those of scores of later authors. Vesalius fully describes the position of the brain; the membranes which cover it; the cavities, or ventricles, within it; the divisions of cerebrum, cerebellum, and medulla; the anatomy of the base, and the origins of the cerebral nerves. These structures are illustrated from different points of view.

The Fifth Book

The fifth book, comprising more than one hundred pages, is devoted to the organs of nutrition. Here we find an admirable account of the peritoneum, the mesentery, the omentum, the stomach and intestines, the liver, the spleen, and the genito-urinary tract—all of which structures are described and fully illustrated. In this book Vesalius also describes the foetus in utero.

The Sixth Book

In less than fifty pages Vesalius describes the contents of the thorax. He writes intelligently of the membrane lining the thorax, and then gives an account of the arteria aspera, as the trachea was formerly named. Passing on to the lungs, he next takes up the anatomy of the heart. He describes its position, form, and structure in better terms than had been done by preceding anatomists. The auricles, ventricles, and valves are carefully examined. His illustrations of both lungs and heart are excellent.

In the 1543 edition of the Fabrica, Vesalius adopts the erroneous view of Galen that openings exist in the septum of the heart. In the second edition of his book, published in 1555, he says that influenced by the views of Galen, he believed that the blood passes from the right to the left ventricle of the heart, through the septum, by means of the pores. Vesalius immediately adds that the septum of the heart is as dense and compact as the rest of this organ, and that not the smallest quantity of blood passes through the septum.

His account of this subject is best given in his own words:—“In recounting as above the structure of the heart, and the use of its different parts, I have followed in the main the doctrines of Galen; not that I regard them in all particulars as consonant with the truth, but because, in attributing new functions and uses to a number of parts, I am still distrustful of myself, and not long ago should hardly have ventured to differ from that Prince of Physicians by so much as a finger’s breadth. As for the dividing wall, or septum, between the ventricles forming the right side of the left cavity, the student of anatomy should consider carefully that it is equally thick, compact, and dense, with all the rest of the cardiac substance enclosing the left ventricle. And accordingly, notwithstanding what I have said about the pits in this situation, and at the same time not forgetting the absorption by the portal vein from the stomach and intestines, I still do not see how even the smallest quantity of blood can be transfused, through the substance of the septum, from the right ventricle to the left”.

Vesalius and other anatomists knew of the hepatic circulation, or at least believed in some communication between the portal and hepatic veins:—“The branches of this vein”—vena cava—“distributed through the body of the liver, come in contact with those of the portal vein; and the extreme ramifications of these veins inosculate with each other, and in many places appear to unite and be continuous”.

Vesalius knew that in several particulars the accepted physiology of the vascular system was wrong. If he could have lived a few years longer, it is possible that he might have solved the great problem which was made clear by William Harvey. In the light of our present knowledge some of Vesalius’s words are suggestive:

“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.

Portal has paid a splendid tribute to Vesalius. “Vesalius”, he says, “appears to me one of the greatest men who ever existed. Let the astronomers vaunt their Copernicus, the natural philosophers their Galileo and Torricelli, the mathematicians their Pascal, the geographers their Columbus, I shall always place Vesalius above all their heroes. The first study of man is man. Vesalius has this noble object in view, and has admirably attained it; he has made on himself and his fellows such discoveries as Columbus could make only by travelling to the extremity of the world. The discoveries of Vesalius are of direct importance to man; by acquiring fresh knowledge of his own structure, man seems to enlarge his existence; while discoveries in geography or astronomy affect him but in a very indirect manner”.

Like Harvey, Vesalius was obliged to defend his writings from fierce attacks. The most desperate of his opponents was his old master, Jacobus Sylvius, who was so wedded to the Galenic teachings that he asserted that since Galen’s time the thigh bones had changed their shape. He spoke of Vesalius as a “madman, Vesanus, whose pestilential breath poisons Europe”. Ponderous discussions were carried on between the friends and opponents of the great anatomist. The complete overthrow of the Galenists resulted.