ON THE MOTION OP THK BLOOD. 71 



it is absurd to refer the motion of the blood through 

 living canals, to the mere mechanical laws of water 

 moving in an hydraulic machine. I have never ob- 

 served this peculiarity of the globules. My persuasion 

 is still more certain that the globules pass on with the 

 other constituents of the blood, and are not rotated 

 around their own axis, — that besides the progressive, 

 there is no intestine, motion in the blood ; although in- 

 deed there can be no doubt that the elements of this 

 fluid are occasionally divided, where it is variously 

 impelled according to the different direction, division, 

 and anastomoses of the vessels. 



121. The powers of the sanguiferous system are now 

 to be examined : first, those of the heart, by far the 

 greatest of all ; afterwards, those which are only sub- 

 sidiary, though indeed highly useful. 



122. That the powers of the heart cannot be accu- 

 rately calculated is clear, upon reflecting that neither 

 the volume of the blood projected at each pulsation, 

 nor the celerity nor distance of its projection, much 

 less the obstacles to the powers of the heart, can be 

 accurately determined. 



123. A rough calculation may be made by taking 

 every probable conjecture together: v. c. if the mean 

 bulk of the blood is considered as 10 pounds, or 120 

 ounces ; the pulsations 75 in a minute, or 4500 in an 

 hour ; and the quantity of blood expelled from the left 

 ventricle at each contraction, as two ounces; it fol- 

 lows that all the blood must pass through the heart 

 75 times every hour. The impetus of the blood pass- 

 ing from the heart, may be conceived by the vio- 

 lence and altitude of the stream projected from a 

 large wounded artery situated near it. I have seen 



