542 THE BLOOD-VASCULAR SYSTEM. 



Ulnar Artery (Fig. 305). 



The Ulnar Artery, the larger of the two terminal branches of the brachial, com- 

 mences a little below the bend of the elbow, and crosses obliquely the inner side of 

 the forearm, to the commencement of its lower half; it then runs along its ulnar 

 border to the wrist, crosses the annular ligament on the radial side of the pisiform 

 bone, and immediately beyond this bone divides into two branches which enter into 

 the formation of the superficial and deep palmar arches. 



Relations in the Forearm. In its upper half it is deeply seated, being covered 

 by all the superficial Flexor muscles, excepting the Flexor carpi ulnaris ; the 

 median nerve is in relation with the inner side of the artery for about an inch and 

 then crosses the vessel, being separated from it by the deep head of the Pronator 

 radii teres ; it lies upon the Brachialis anticus and Flexor profundus digitorum 

 muscles. In the lower half of the forearm it lies upon the Flexor profundus, being 

 covered by the integument, the superficial and deep fasciae, and is placed between 

 the Flexor carpi ulnaris and Flexor sublimis digitorum muscles. It is accompanied 

 by two venae comites ; the ulnar nerve lies on its inner side for the lower two- 

 thirds of its extent, and a small branch from the nerve descends on the lower part 

 of the vessel to the palm of the hand. 



PLAN OF RELATIONS OF THE ULNAR ARTERY IN THE FOREARM. 



In front. 



Superficial laver of flexor muscles. ) T T , ,n 

 Median nerve. j Upper halt 



Superficial and deep fasciae. Lower half. 



Inner site. Ulnar Outer side 



Behind. 



Brachialis anticus. 



Flexor profundus digitorum. 



At the wrist (Fig. 304) the ulnar artery is covered by the integument and fascia, 

 and lies upon the anterior annular ligament. On its inner side is the pisiform bone. 

 The ulnar nerve lies at the inner side, and somewhat behind the artery ; here the 

 nerve and artery are crossed by a band of fibres, which extends from the pisiform 

 bone to the anterior annular ligament. 



Peculiarities. The ulnar artery has been found to vary in its origin nearly in the propor- 

 tion of one in thirteen cases, in one case arising lower than usual, about two or three inches 

 below the elbow, and in all other cases much higher, the brachial being a more frequent source 

 of origin than the axillary. 



Variations in the position of this vessel are more frequent than in the radial. When its 

 origin is normal the course of the vessel is rarely changed. When it arises high up it is almost 

 invariably superficial to the flexor muscles in the forearm, lying commonly beneath the fascia, 

 more rarely between the fascia and integument. In a few cases its position was subcutaneous 

 in the upper part of the forearm, subaponeurotic in the lower part. 



Surface Marking. On account of the curved direction of the ulnar artery the line on the sur- 

 face of the body which indicates its course is somewhat complicated. First, draw a line from the 

 front of the internal condyle of the humerus to the radial side of the pisiform bone ; the lower 

 two-thirds of this line represents the course of the middle and lower third of the ulnar artery. 

 Secondly, draw a line from the centre of the hollow in front of the elbow-joint to the junction of the 

 upper and middle third of the first line ; this represents the course of the upper third of the artery. 



Surgical Anatomy. The application of a ligature to this vessel is required in cases of 

 wound. of the artery or of its branches, or in consequence of aneurism. In the upper half of 

 the forearm the artery is deeply seated beneath the superficial flexor muscles, and the applica- 

 tion of a ligature in this situation is attended with some difficulty. An incision is to be made 

 in the course of a line drawn from the front of the internal condyle of the humerus to the outer 

 side of the pisiform bone, so that the centre of the incision is three fingers' breadth below the 

 internal condyle. The skin and superficial fascia having been divided and the deep fascia 

 exposed, the white line which separates the Flexor carpi ulnaris from the other flexor muscles 



