Vesalius regarded the Fabrica as the gospel of a new approach to human anatomical studies and a new method of anatomical investigation. In Padua both the gospel and its explications were presented directly by the author. For those elsewhere it was presented through the Fabrica with its long and complete descriptions, its illustrative and diagrammatic guides to aid recognition of details and to supplement the reader’s possible shortage of dissection specimens, and even its indirect encouragement of body snatching if necessary. The work reflects fully Vesalius’ method of instruction from about the end of 1539 through 1542 and represents some of it pictorially on the title page.
The presentation of a new anatomy and anatomical method raised several problems, of which the first was that of terminology. As in the Tabulae anatomicae (1538), Vesalius continued to use terms from several languages but stressed the Greek form wherever possible. If this was not enough for clarity, an extensive description was given to localize the part with reference to other parts, and illustrations of the particular organ or structure were provided. Additionally, as a mnemonic device and for increased comprehension, anatomical structures were related to common objects, the radius, for example, being compared to the weaver’s shuttle and the trapezius muscle to the cowl of the Benedictine monks. Some of Vesalius’ terms are still in use, so that this aspect of his pedagogy plays the same role today as it did in the sixteenth century. Thus the names of two of the auditory ossicles, the incus and malleus, are derived from vesalius’ description of them as “that one somewhat resembling the shape of an anvil [incus]” and “that one resembling a hammer [malleus].” The valve of the left atrioventricular orifice, the mitral valve, “you may aptly compare to a bishop’s miter.”
Vesalius’ greatest contribution to the elucidation of anatomy is to be found in the illustrations to the Fabrica. With the exception of those few diagrammatic illustrations that are known to have been drawn by him there is no positive identification of individual draftsmen. The soundest theory is that they were students from Titian’s studio in Venice. Possibly among them was Jan Stephen of Calcar, who drew the three figures of the skeleton for the published version of Vesalius’ anatomical plates of 1538; but the three skeletons of the Fabrica are so greatly superior to those of the earlier work that it seems unlikely that Calcar was responsible for them.
The anatomical detail of the illustrations and their numbered and lettered explanatory legends make it clear that the drawings were made under the supervision of Vesalius for the specific purpose of clarification of a particular portion of the text. Not only is the quality of draftsmanship and precision of detail immensely superior to that of earlier books but the marginal references to the illustrations, which in some instances relate a textual description to several illustrations located in different parts of the work, are also entirely without precedent. For the first time the pedagogic purpose of illustrations was achieved—so well that unfortunately attention has more recently been centered upon the illustrations to the exclusion of the text, thereby nullifying Vesalius’ purpose and even damaging his reputation. He has, for example, been criticized for the exaggerated upward extension of the rectus abdominis muscle as it appears in the fifth “muscle man,” although the legend accompanying the illustration explains this as having been done deliberately to represent an error of Galenic anatomy. Several such seeming errors are in fact deliberate distortions serving pedagogical purposes; they are not appreciated, however, unless text and illustrations are studied together.
In addition to the title page the most noteworthy illustrations in the Fabrica are the three celebrated skeletal figures and the series of “muscle men” which through their postures were given a dynamic quality that was intentional and specifically referred to by Vesalius. The “muscle men,” shown from the front, side, and back, and displaying in sequence from the surface downward the underlying layers of muscle, were a novelty, although crudely foreshadowed by the series of figures in Berengario da Carpi’s Commentaria (1521); the latter, however, were wholly lacking the elegance and detail to be found in the Vesalian figures.
Owing to the larger amount of dissection material available to him, Vesalius was not compelled to follow the traditional pattern of dissection and description originally established by Mondino (1316). Consequently, book I of the Fabrica opens with a description of the bones. This arrangement was desirable since according to Vesalius the bones are the foundation of the body, the structure to which everything else must be related; and in his anatomical demonstrations he was accustomed to sketch the position of the bones on the surface of the body with charcoal in order to orient the students. The fundamental significance of the bones was further indicated by his reference to the femur, for example, as either the bone itself or the entire leg of which the bone was the basic structure. Moreover, the bones are not only supports for the body; since by their structure and formation they assist and control movement, it is necessary to recognize in them a dynamic quality that Vesalius sought to emphasize by the suggestion of movement in the poses of the skeletons.
The teleological argument that pervades the Fabrica, an inheritance from Galen, is very pronounced in the description of osteology. “By not first explaining the bones anatomists… deter [the student] from a worthy examination of the works of God.” Vesalius did not allow this doctrine of final causes to control his investigations, however, since unlike his medieval predecessors he sought to discover first structure and related function, and only then the ultimate purpose.
In his description of human osteology, the subject of book I, Vesalius made some of his strongest assaults upon Galenic anatomy. He called attention to Galen’s false assertion that the human mandible is formed of two bones and demonstrated the significance of this error as reflecting a dependence upon animal sources. Likewise he pointed to the fact that the Galenic description of the sternum as formed of seven segments is true of the ape but not of the adult human sternum, which has only three. Similarly the “humerus, according to Galen, is with the exception only of the femur, the largest bone of the body. Nevertheless the fibula and tibia are distinctly of greater length than the humerus.” In addition to such criticisms, there is extensive description of osteological detail, which, because much of it was wholly novel, required detailed illustrations, elaborately related by letter and number to the text. Despite some errors of description and occasional references to animal anatomy in the Galenic tradition, this first book represents Vesalian anatomy on the highest level. It concludes with a remarkable chapter on the procedure for preparation of the bones and articulation of the skeleton, since it was essential that a skeleton always be available at the dissection. Such a skeleton is a central figure of the title page.
As he had done with the bones, so Vesalius endeavored in book II to identify and give the fullest possible description of every muscle and its function; and an examination of the “muscle men” indicates the thoroughness with which that task was performed. Unfortunately, his system of identifying muscles numerically according to the part they served was cumbersome in comparison with the method of identification by origin and insertion introduced by Sylvius in 1555 and later revised and improved by the Swiss anatomist Gaspard Bauhin. The first two books represent the major Vesalian achievement in terms of accuracy of description and present the most telling blows against Galenic anatomy. In book II Vesalius also most frequently provided chapters dealing with the dissection procedure used to arrive at his conclusions. The description of the vascular system in book III is less satisfactory because of Vesalius’ failure to master the complexities of distribution of the vessels and because of the close relationship of the vascular system to Galenic physiology. Vesalius was compelled to subscribe to this for lack of any other theories. The errors in the Vesalian description of the distribution of the vessels are due to his reliance on Galen, as the only other writer to have attempted such a description in detail, and to the difficulty of discovering anew the entire vascular arrangement in rapidly putrefying human material. Although Vesalius was partly successful, as, for example, in his account of the interior mesenteric and the hemorrhoidal veins, there are many indications that he was compelled to rely for much of his account on the anatomy of animals. This is clearly apparent in the illustration of the “arterial man,” where the arrangement of the branchings of the aortic arch actually illustrate simian anatomy.
Book IV provides an account of the nervous system. It is introduced by an attempt to clarify and limit the meaning of the word “nerve” to the vehicle transmitting sensation and motion, because “leading anatomists declare that there are three kinds of nerve” : ligament, tendon, and aponeurosis. “From dissection of the body it is clear that no nerve arises from the heart as it seemed to Aristotle in particular and to no few others.” Although Vesalius was obliged to accept the Galenic explanation of nervous action as induced by animal spirit distributed through the nerves from the brain, his examination of the optic nerve led him to the conclusion that the nerves were not hollow, as Galen had asserted. “I inspected the nerves carefully, treating them with warm wate