EXPEEIMEXTATION AND PHYSIOLOGY 



he was correct. He learned of the action of 

 the heart, and the propulsion of the blood 

 away from the heart through the arteries and 

 its return to the heart through the veins, by his 

 dissections of living and recently dead animals. 

 The study of the blood-vessels of dead animals 

 had deceived investigators for two thousand 

 years. When he finally announced his dis- 

 covery it met with strenuous opposition, and 

 its correctness was a matter of discussion for 

 twenty-five years. 



How the blood passed from the arteries to 

 the veins was not known to Harvey. Malpigi 

 (1661), the founder of pathologic anatomy, 

 discovered the capillary circulation. The con- 

 clusive demonstrations remained for Leeuwen- 

 hoeck (1674) who, with his microscope, ac- 

 tually saw the blood cells streaming along in 

 the capillaries in the web of a frog's foot spread 

 out upon the stage of his microscope. This 

 was one of the earliest uses of the microscope, 

 and completed the chain of evidence, which 

 established the knowledge of the circulation. 



By experiments upon living animals Galen, 

 about 200 A. D., discovered that the arteries 

 contain blood; Harvey, after fifteen hundred 

 years, discovered the motion of the heart, 



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