THE CONQUEST OF DISEASE 



Later 

 studies of 

 the blood. 



Transfu- 

 sion and 

 infusion. 



blood, for three-quarters of a century longer, 

 when the mechanics of the circulation were 

 worked out again independently by Harvey, 

 who knew nothing of the labors of Servetus. 



Following Harvey, there came a steady 

 series of additions to physiologic knowledge 

 based on the study of living animals. Blood 

 pressure was first studied by Stephen Hales 

 ( 1727) . He introduced a long glass tube into 

 a blood vessel of a living animal and observed 

 the height to which the blood column rose. To 

 the femoral artery of a horse he attached a 

 tube nine feet long. These experiments showed 

 the contractile power and elasticity of the 

 arteries, a knowledge of which is quite as im- 

 portant as a knowledge of the contractile 

 power of the heart in order to understand the 

 motive force which propels the blood stream. 

 The experiments in the transfusion of blood 

 were made upon animals before being applied 

 to man. As early as 1556 Cardanus had sug- 

 gested transfusion. Potter in England (1638) 

 experimented upon animals with this oper- 

 ation, being stimulated by Harvey's dis- 

 covery. Boyle and Lowes conducted similar 

 experiments, bleeding animals and then rein- 

 troducing into their vessels blood from other 



