BIOLOGY AND MEDICINE—CHANDLER 319 
that they had undergone a change in the intervening centuries due 
to the habit of wearing tight trousers. 
The study of anatomy was retarded greatly by religious and civic 
taboos on dissection of human bodies, but Vesalius spirited skeletons 
from beneath gallows and was not above occasional clandestine disin- 
terments. He made important contributions to human anatomy, and 
did much to start other physicians consulting nature instead of Galen. 
Vesalius even reached the threshold of the discovery of the circulation 
of the blood, but this great milestone in the history of medicine was 
planted by Harvey in the seventeenth century. Probably no other 
single physiological discovery has had such profound consequences. 
What a superlative.age that was, to produce a Harvey, a Shakespeare, 
and a Galileo! 
In the eighteenth century advances were more rapid. It was in 
that century that another great Englishman, John Hunter, discovered 
that if arteries are tied off the blood will find and develop new chan- 
nels. Prior to that discovery aneurisms, which were distressingly 
common, were treated, if at all, by amputation of limbs. John Hunter 
also learned some of the tricks of grafting skin and bones. 
In the next century, the nineteenth, two other fundamental bio- 
logical principles—the cellular structure of bodies, and evolution— 
came to light. Both of these ideas contribute so much to our knowl- 
_ edge of the human body and how it works that a full evaluation of 
their significance in medicine would be almost impossible. 
Even with all these advances in anatomy and physiology, nobody 
up to the middle of the seventeenth century had any good idea what 
disease was or whence it came. An important forward step was made 
in 1687 when two Italian scientists, Bonomo and Cestoni, showed that 
scabies was a disease caused by tiny mites burrowing and reproducing 
in the skin, and was spread by transmission of the mites. This was the 
first demonstration of a specific cause for a disease, and the first ex- 
planation of its spread, and was a clean break from the divine, 
humoral, or other ancient theories of the spontaneous origin of disease. 
A few pioneering minds, a century or two ahead of their times, 
propounded theories of contagion, and spread of disease by dessemina- 
tion of poisonous particles or gases, or even by invisible living organ- 
isms, but there was no experimental evidence, and these precocious 
ideas fell on barren ground. A true understanding of infectious dis- 
ease had to wait for the discovery of micro-organisms and some knowl- 
edge of their nature. 
Leeuwenhoek, a Dutch lens grinder of the seventeenth century, 
who invented a compound microscope capable of bringing bacteria 
within the range of visibility, is sometimes called the father of bac- 
teriology, but I think he might more properly be called its midwife. 
He was one of the greatest explorers of all time. Magellan and 
