Skeletal system • Vesalius believed the
skeletal system to be the framework of the human body. It was in this opening chapter or book of
De fabrica that Vesalius made several of his strongest claims against
Galen's theories and writings which he had put in his anatomy books. In his extensive study of the skull, Vesalius claimed that the
mandible consisted of one bone, whereas Galen had thought it to be two separate bones. He accurately described the
vestibule in the interior of the
temporal bone of the skull. • In
Galen's observation of the ape, he had discovered that their
sternum consisted of seven parts which he assumed also held true for humans. Vesalius discovered that the
human sternum consisted of only three parts. • He also disproved the common belief that men had one rib fewer than women and noted that the
fibula and
tibia bones of the leg were indeed larger than the
humerus bone of the arm, unlike
Galen's original findings.
Muscular system • One of Vesalius' contributions to the study of the
muscular system is the illustrations that accompany the text in
De fabrica, which would become known as the "muscle men". He describes the source and position of each muscle of the body and provides information on their respective operation.
Vascular and circulatory systems • Vesalius' work on the
vascular and
circulatory systems was his greatest contribution to modern medicine. In his dissections of the heart, Vesalius became convinced that Galen's claims of a porous
interventricular septum were false. This fact was previously described by
Michael Servetus, a fellow of Vesalius, but never reached the public, for it was written down in the "Manuscript of Paris", in 1546, and published later in his
Christianismi Restitutio (1553), a book regarded as heretical by the
Inquisition. Only three copies survived, but these remained hidden for decades, the rest having been burned shortly after publication. In the second edition Vesalius published that the septum was indeed waterproof, discovering (and naming), the
mitral valve to explain the blood flow. • Vesalius believed that
cardiac systole is synchronous with the
arterial pulse. • He not only verified
Estienne's findings on the valves of the
hepatic veins, but also described the
azygos vein, and discovered the canal which passes into the fetus between the
umbilical vein and
vena cava.
Nervous system • Vesalius defined a nerve as the mode of transmitting sensation and motion and thus refuted his contemporaries' claims that
ligaments,
tendons and
aponeuroses were three types of nerve units. • He believed that the brain and the nervous system are the center of the mind and emotion in contrast to the common
Aristotelian belief that the heart was the center of the body. He correspondingly believed that nerves themselves do not originate from the heart, but from the brain—facts already experimentally proved by
Herophilus and
Erasistratus in the classical era, but suppressed after the adoption of Aristotelianism by the Catholic Church in the Middle Ages. • Upon studying the
optic nerve, Vesalius came to the conclusion that nerves were not hollow.
Abdominal organs • In
De fabrica, he corrected an earlier claim he made in
Tabulae about the right kidney being set higher than the left. Vesalius claimed that the kidneys were not a filter device for urine to pass through, but rather that the kidneys serve to filter blood as well, and that excretions from the kidneys travelled through the
ureters to the bladder. • He described the
omentum, and its connections with the stomach, the spleen and the colon gave the first correct views of the structure of the
pylorus. • He also observed the small size of the
caecal appendix in man and gave the first good account of the
mediastinum and
pleura. • Vesalius admitted that due to a lack of pregnant cadavers he was unable to come to a significant understanding of the reproductive organs. However, he did find that the uterus had been falsely identified as having two distinct sections.
Heart • Through his work with muscles, Vesalius believed that a criterion for muscles was their voluntary motion. On this claim, he deduced that the heart was not a true muscle due to the obvious involuntary nature of its motion. • He also addressed the controversial issue of the heart being the centre of the soul. He wished to avoid drawing any conclusions due to possible conflict with contemporary religious beliefs., showing the
optic chiasma,
cerebellum,
olfactory bulbs, etc. • Against Galen's theory and many beliefs he also discovered that there was no hole in the
interventricular septum or
heart.
Other achievements • Vesalius disproved Galen's assertion that men have more teeth than women. • Vesalius introduced the notion of induction of the extraction of
empyema through surgical means. • Due to his study of the human skull and the variations in its features he is said to have been responsible for the launch of the study of
physical anthropology. • Vesalius always encouraged his students to check their findings, and even his own findings, so that they could better understand the structure of the human body. • In addition to his continual efforts to study anatomy he also worked on medicinal remedies and came to such conclusions as treating
syphilis with
chinaroot. • Vesalius claimed that medicine had three aspects: drugs, diet, and 'the use of hands'—mainly suggesting surgery and the knowledge of anatomy and physiology gained through dissection. • Vesalius was a supporter of 'parallel dissections' in which an animal cadaver and a human cadaver are dissected simultaneously in order to demonstrate the anatomical differences and thus correct Galenic errors. == Scientific and historical impact ==