298 CIRCULATION. [Lesson xxxix. 



tinue (if it be not stopped by art) until, through 

 loss of Blood, the animal faints or dies. But if 

 the same artery be opened between the ligature and 

 extremities, a few drops only will ooze out from 

 the wounded coats. 



On the other hand, when a vein is laid bare, 

 and a ligature made upon it, if it be opened be- 

 tween the ligature and the extremities, the Blood 

 will gush out, as we see in common venesection. 

 But if the same vein be opened between the bind- 

 ing and the heart, no Blood will appear. From 

 these experiments it is obvious to the slightest 

 attention, that the Blood flows from the heart, 

 through the arteries, to the extreme parts of the 

 body; and returns again through the veins to the 

 heart.' 



For the regular performance and continuation 

 of this motion of the Blood through all the dif- 

 ferent parts of the body, the heart, which is the 

 primitm mobile, giving the first impulse, is fur- 

 nished with four distinct muscular cavities, that 

 is, with an auricle and a ventricle on the right 

 side, and an auricle and a ventricle on the left. 

 Through these cavities, curiously adapted to their 

 * respective offices, the Blood circulates in the fol- 

 lowing order : it is received from the veins, first 

 into the right auricle, which, contracting itself, 

 pushes the Blood into the right ventricle at that 

 instant dilated. The moment this ventricle is 

 filled, it contracts itself with great force, and im- 

 pels the Blood into the pulmonary artery, which 

 passing through the lungs, and returning by the 



pulmonary 



