Chap. 12 CIRCULATION AND TRANSPORTATION BODY FLUIDS 223 



lack of microscopes, and arteries seemed to be always empty except for air. 

 In 1628 William Harvey, an English physician, showed that the blood moves 

 "as it were, in a circle." If wc consider the quantity of blood that is thrown 

 out by the heart every min-ute (approximately two ounces times 72 beats), he 

 said, "where can it go unless it circulates?" This argument was set forth in 

 Harvey's great work, De Motii Cordis {On the Motion of the Heart) published 

 in 1628, eight years after the Pilgrims landed in New England. This small book 

 opened the door to modern medical treatment. It is a record of observations 

 and experiments made by an adventurous and reasoning person. 



