MUSCULARITY ~OF ARTERIES. 139 



thus completely closed : in this contracted state it remains 

 for a time, varying from a few hours to two days : then it 

 dilates again, and permanently retains the same size. If, 

 while contracted, the artery be forcibly distended, its con- 

 tractility is destroyed, and it holds a middle or natural size. 



This persistence of the contractile property after death 

 was well shown in an observation of Hunter, which may 

 be mentioned as proving, also, the greater degree of 

 contractility possessed by the smaller than by the larger 

 arteries. Having injected the uterus of a cow, which had 

 been removed from the animal upwards of twenty-four 

 hours, he found, after the lapse of another day, that the 

 larger vessels had become much more turgid than when he 

 injected them, and that the smaller arteries had contracted 

 so as to force the injection back into the larger ones. 



The results of an experiment which Hunter made with 

 the vessels of an umbilical cord prove still more strikingly 

 the long continuance of the contractile power of arteries 

 after death. In a woman delivered on a Thursday after- 

 noon, the umbilical cord was separated from the foetus, 

 having been first tied in two places, and then cut between, 

 so that the blood contained in the cord and placenta was 

 confined in them. On the following morning, Hunter tied 

 a string round the cord, about an inch below the other 

 ligature, that the blood might still be confined in the 

 placenta and remaining cord. Having cut off this piece, 

 and allowed all the blood to escape from its vessels, he 

 attentively observed to what size the ends of the cut arte- 

 ries were brought by the elasticity of their coats, and then 

 laid aside the piece of cord to see the influence of the 

 contractile power of its vessels. On Saturday morning, 

 the day after, the mouths of the arteries were completely 

 closed up. He repeated the experiment the same day with 

 another portion of the same cord, and on the following 

 morning found the results to be precisely similar. On the 

 Sunday he performed the experiment the third time, but 



