170 CIRCULATORY SYSTEM. 



a coagulum has been produced by ligature, it is finally ab- 

 sorbed. 



The Nerves of the arteries, according to Wrisberg and Be- 

 clard, are numerous and considerable, form around them a plex- 

 us resembling that of the par vagum around the oesophagus, and 

 follow them into the interior of our organs, with the exception 

 of the brain; which has them only to its surface. They are 

 proportionately more abunSant in the aortic than in the pulmo- 

 nary ^system; also upon the smaller than upon the larger arte- 

 ries. The arteries of the head, of the neck, of the thorax, and 

 of the abdomen, are supplied from the sympathetic nerve, while 

 those of the extremities are supplied from the nerves of the spi- 

 nal marrow. 



The passing of the blood through the arteries is accompanied 

 with a pulsating motion, 'which, for the most part, is exactly 

 synchronous with the contraction of the left ventricle, and de- 

 pends upon an increased quantity of blood thrown into them at 

 the moment. The dilatation of the artery may be both seen and 

 felt: "but were we to judge of the real increase of the artery 

 by this, we should deceive ourselves; for when covered by in- 

 teguments, the apparent effect is much greater than it really is 

 in the artery itself; for in laying such an artery bare, the nearer 

 we come to it, the less visible is its pulsation; and, when laid en- 

 tirely bare, its motion is hardly either to be seen or felt. This 

 apparent diastole of the artery is augmented in proportion to the 

 solid matter covering it, whence tumours over large arteries 

 have considerable motion given to them, and have often been 

 supposed to be aneurismal. Arteries, in fact, during their dias- 

 tole or dilatation, increase much more in length than in width, 

 and are thrown into a serpentine course: instead, therefore, ot 

 the term diastole, it should rather be called the elongated state."* 

 Mr. Parry, of Bath,f has denied that the arteries dilate at a-11 

 during their diastole: his opinion however, is peculiar, though, 

 in an experiment performed some years ago upon the carotid 

 artery of a calf, its correctness appeared to me then to be fully 

 proved. 



There is no part of the human body which presents more fre- 

 quent varieties, in different individuals, than the arteries. These 



* J. Hunter, loe. cit. f Experimental Inquiry on the Pulse, 18161819 



