142 VITAL FUNCTIONS. 



pie of the pure juice of the grape contained about 14 

 per cent, of alcohol. 



Muscular force of the Heart. Some of the old 

 physiologists attempted to compute in numbers, the force 

 of the muscular contractions of the heart, but this ap- 

 pears to be impracticable, and if it could be done, would 

 present a mere physiological curiosity. That the heart 

 contracts with an enormous power, when compared 

 with its size as a muscle, there is no doubt. The obsta- 

 cles it has to overcome in dilating the contractile tenden- 

 cy of the arteries through all their ramifications, must 

 alone require a very considerable force. It must be 

 remembered, that it requires a much greater mechani- 

 cal force to propel a fluid through an angular or tortuous 

 tube than through a straight one ; and that few of the 

 arteries run in a direct course, many of them making a 

 full semi-circle in passing from the heart to the other 

 parts of the system. This may be observed on view- 

 ing the plans of the heart, where it will be seen that the 

 great circle of the aorta must materially impede the ve- 

 locity of the blood through it. But notwithstanding 

 these obstacles, we find that the force of the blood 

 through the arteries, even in the extremities, is so great, 

 that when we sit cross-legged, the pulsation of the artery 

 in the ham, which is pressed by the under knee, is so 

 strong as to raise the whole extremity, and give it a vibra- 

 tory motion at each beat of the heart. When we consider 

 the length of the lever, the shortness of the purchase, 

 and the elastic nature of the fulcrum, we cannot but be 

 astonished at the prodigious force with which the heart 

 must contract, in order to give such power, at such a 

 distance, to a little artery not larger than'a pipe stem. 



Operative surgeons are well aware of this contractile 

 force, when they have to do with wounded arteries, for 

 in most cases it is found that compression is entirely in- 

 adequate to bring the sides of an artery into such con- 

 tact as to stop the bleeding, and even ligatures, if not 



What is said of the power with which the heart contracts? What 

 proofs are given of this contractile power 1 



