138 VITAL FUNCTIONS. 



sample of the pure juice of the grape contained about 14 

 per cent, of alcohol. 



410. 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 appears 

 to be impracticable, and if it could be done, would pre- 

 sent a mere physiological curiosity. That the heart con- 

 tracts with an enormous power, when compared with its 

 size as a muscle, there is no doubt. The obstacles it has 

 to overcome in dilating the contractile tendency of the 

 arteries through all their ramifications, must alone re- 

 quire a very considerable force. It must be remembered, 

 that it requires a much greater mechanical force to pro- 

 pel 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 viewing the plans of 

 the heart, where it will be seen that the great circle of 

 the aorta must materially impede the velocity 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, arid give it a vibratory 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 prodi- 

 gious 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. 



411. Operative surgeons are well aware of this con- 

 tractile force, when they have to do with wounded arte- 

 ries, for in most cases it is found that compression is en- 

 tirely inadequate to bring the sides of an artery into such 

 contact 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 ? 



