LECTURE V. 231 



ries, are calculated to produce a rapid cur- 

 rent of the blood through the larger vessels, 

 in order that it may arrive unchanged at the 

 part for the supply of which it is designed; 

 and that other circumstances there occur- 

 ring, are intended to retard its motion, so 

 that it may be modified and rendered sub- 

 servient to the purposes of secretion and 

 nutrition. 



Now you know, Gentlemen, that some 

 physiologists suppose the velocity of the 

 current of blood to be equal in all sets of 

 vessels. With respect to this subject, I will 

 merely refer you to an experiment of Hales, 

 in his Hsemastatics. Having estimated the 

 probable force of the heart, he put a tube 

 into the aorta of a dead dog, and kept it 

 filled with water to a height which would 

 give an equal propulsion to the supposed 

 power of the heart. Under these circum- 

 stances, having opened the abdomen, he 

 cut along the tube of the intestines, at 

 that part most remote from the mesentery, 

 and observed the water running tardily 

 from the orifices of the divided arteries. 



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