8 



ZOOLOGY AS A SCIENCE 



sis for medical knowledge for the next 1,200 

 years. His book, On Anatomical Prepara- 

 tions, was the standard medical text during 

 this long period, perhaps the longest "run" 

 any textbook has ever enjoyed. 



In the next twelve centuries authority as 

 a source of all information reached its peak. 

 This was very well illustrated in the study 

 of medicine. The professor of anatomy, for 

 example, sat before his class with a large 

 volume of Galen's text before him, and a 

 human body, when it was available, dis- 

 played on the dissecting bench some 

 distance below. A barber or two huddled 

 over the body, exposing the various parts, 

 as the professor read about them from the 

 text. The students looked on and absorbed 

 what they could from this crude demonstra- 

 tion. The unquestioning faith in authority 

 of this period was revealed when some por- 

 tion of the human body did not agree with 

 the description in Galen; the body was al- 

 ways considered at fault, not the text. Such 

 mistakes were common, since Galen's dis- 

 sections were based on animals other than 

 man. This was typical of the time, even in 

 learned circles, and this profound respect 

 for authority persisted until a few bold men 

 dared strike out to see and learn for them- 

 selves some centuries later. 



Among the many men who had the abil- 

 ity and courage to fight blind ignorance was 

 Vesalius, who was born in Brussels ( 1514), 

 trained for medicine in Paris, and finally 

 became professor of medicine at Padua in 

 Italy at 22 years of age. During his early 

 medical school days he was a devoted fol- 

 lower of Galen's teachings. But Vesalius was 

 able to secure human bodies for dissection, 

 and as he probed more deeply into the 

 details of human anatomy he discovered 

 Galen's errors. Being an independent 

 thinker, he soon decided that he must write 

 down his own observations concerning hu- 

 man anatomy without reference to the work 

 of anyone else. He secured the services of 

 some of the best artists of his day to illus- 



trate the book that he felt the urge to write. 

 Some recently discovered wood-cuts made 

 by Calcar, a student of Titian, were found 

 to be as beautiful as when first used in 

 Vesalius' book. On the Structure of the Hu- 

 man Body (Figs. 1-3 and 4). Because he 

 was at variance with Galen, Vesalius soon 

 became the subject of much adverse criti- 

 cism, which finally forced him to leave his 

 professorial post to become court physician 

 for Emperor Charles V. In this position he 

 apparently was not happy, because some 

 years later he left on a pilgrimage to Jeru- 

 salem from which he never returned. 



The greatest contribution this energetic 

 man made to the world was his break away 

 from authority and his reestablishment of 

 the old Aristotelian ideal of pursuing the 

 answer to problems by direct observations. 

 This revolt from authority was furthered by 

 others after Vesalius, but it received its 

 greatest impetus from William Harvey 

 ( 1578 ) , a British physician, who gave us 

 the first experimental approach to biological 

 problems. Educated at Padua, Vesalius' old 

 school, Harvey became interested in the 

 blood vascular system, and went to work 

 eagerly after he left the university, to learn 

 more about this perplexing problem. Up to 

 his time the heart was thought to be purely 

 passive and non-muscular; the blood was 

 supposed to flow into the heart causing it 

 to expand suddenly, which accounted for 

 its audible beat against the thorax. The 

 blood somehow picked up that intangible 

 "spiritus vitalis" while in the heart, then 

 passed to the liver where the food was 

 changed into blood, thus nourishing the 

 body. 



Harvey demonstrated that the heart was 

 a muscular organ and that its contractions 

 were responsible for propelling the blood 

 through the arteries. He experimented with 

 animals and studied normal and abnormal 

 humans for twenty years before he was cer- 

 tain that the blood flowed away from the 

 heart in the arteries, and returned to the 



