MOTION OF THE HEART AND BLOOD 



Further, if the pulmonary artery, a large vessel, 

 with heavy arterial walls, be destined for only the 

 single particular purpose of nourishing the lungs, 

 why should the pulmonary vein, scarcely of the 

 same size, with soft flabby venous walls, be supposed 

 to have three or four different uses? It is desired 

 that air pass through this vessel from the lungs to 

 the left ventricle, likewise that waste vapors escape 

 by the same vessel from the heart to the lungs, and 

 that some of the spiritous blood from the heart be 

 distributed by it to keep the lungs alive. 



To desire that waste vapors from the heart and 

 air to the heart be transmitted by this same conduit 

 is opposed to Nature which nowhere has made but 

 a single vessel or way for such contrary movements 

 and purposes. 



If waste vapors and air come and go by this pas- 

 sage, as they do in the pulmonary bronchi, why do 

 we find neither air nor sooty vapors when we cut 

 open the pulmonary vein ? Why do we always find 

 the pulmonary vein full of thick blood, never of air, 

 while in the lungs we note plenty of air? 



If one repeats Galen's experiment of opening the 

 trachea of a living dog, forcing air into the lungs by 

 a bellows, and then firmly tying off the trachea, a 

 great abundance of air even out to the pleurae will 

 be found in the lungs on opening the chest. No air, 

 however, will be found in the pulmonary vein or in 

 the left ventricle of the heart. It certainly should 

 be if the heart drew in air from the lungs, or if the 



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