15'^ Proceedings of the Ohio State .Icademy of Science 



monary circulation. He arrives at this conclusion from his 

 estimate of the amount of bloo(l in the body, and that arteries 

 would become congested if there was no way for it to get out 

 .)! the arteries ; the body could not use up the blood as fast as 

 it was made or absorbed from the viscera, therefore the blood 

 must travel in a circle from the left side of the heart through 

 the arteries of the tissues from the tissues to the veins 

 through them to the right side of the heart, through the pul- 

 monary artery to the lungs, through the pulmonary vein tn 

 the left side of the heart. In other words the blood must 

 travel in a circle. He savs : "I frequentlv and serioush- be- 

 thought me. and long revolved in my mind, what might bo 

 the quantity of blood which was transmitted, in how short a 

 time its passage might be affected, and tlie like; and not find- 

 ing it possible that this could be supplied by the juices of the 

 ingested aliment without the veins on the one hand becoming 

 drained, and the arteries on the other hand Ijecoming rup- 

 tured through the excessive charge of blood, unless the bkM)d 

 should somehow find its way from the arteries into the veins, 

 and so return to the right side of the heart; I began to think 

 whether there might be a motion, as it were, in a circle. Xow 

 this I afterwards found to be true : and I finally saw tliat the 

 l)lood. forced by the action of the left ventricle into the ar- 

 teries, was distributed to the body at large, and its several 

 parts, in the same manner as it is sent througli the lungs, 

 impelled by the right ventricle into the ])ulmonary artery and 

 tliat It then passed through the veins and along the vena cava 

 and so round to the left \entriclc in the manner already in- 

 dicated, which motion we may be allowed to call circular." 



The heart is emptied when the vena ca\a is tied, the vena 

 cava becomes distended when the aorta is tied, the limb be- 

 comes swollen when a tight ligature is sui)])lied to slmt ofi" 

 the veins, the same limb becomes ])ale when a tight ligature 

 is a])plied to shut off the arteries, nearly all of the 1)lood in 

 the body can be drained away from a single opening in a 

 vein. All of this can be easih- understood in the light of 



