EADIAL AND ULNAE AETEEIES. 267 



communication between the superior and inferior thyroid arteries, 

 the ligature upon the external carotid should be placed distally 

 to the origin of the superior thyroid, so that no blood may be 

 brought from the subclavian through the thyroid axis and its 

 inferior thyroid branch to the superior thyroid, and so to the site 

 of haemorrhage. This anastomosis, and the danger of interfering 

 with the blood supply of the brain, are the reasons why under 

 these circumstances it is better to ligature the external rather 

 than the common carotid artery. 



In cut- throat injuries the vessels frequently escape any damage. 

 This is chiefly because their position is at a posterior plane in 

 consequence of the projection forwards of the thyroid cartilage, 

 by which structure they are protected when the cut is made as 

 high up as it generally is. 



Arteries of the Upper Extremity. It is uncommon to get 

 injuries of any of the arterial trunks except those in the lower 

 part of the forearm. The radial and the ulnar close above the 

 wrist are frequently divided in association with the other 

 structures, especially in such injuries as occur from the hand 

 having been thrust through a pane of glass. 



The radial artery lies on the radial side of the flexor carpi 

 radialis tendon, and, being quite superficial, can be easily picked 

 up and ligatured, if necessary, after some enlargement of the 

 wound. 



The ulnar artery is somewhat more deeply placed, lying to the 

 radial side of the flexor carpi ulnaris tendon, and it is well to 

 recollect the close proximity of the ulnar nerve, which is placed 

 between the artery and the tendon, for the nerve may be damaged 

 at the same time that the artery is severed. 



Punctured wounds of the palm of the hand may involve one or 

 other of the palmar arches. The superficial palmar arch, formed 

 as a rule by the superficial branch of the ulnar being joined by 

 the superficial volar of the radial, has its lowest point of con- 

 vexity at the level of the fully outstretched thumb. A wound of 

 this arch can be readily dealt with by ligature after an incision 

 through the palmar fascia. 



