THE SUPEKFICIAL PALMAR ARCH. 



447 



where they are joined by the palmar interosseous arteries from the deep arch, and 

 by inferior perforating arteries from the back of the hand. On the sides of the 

 fingers, each collateral artery lies beneath the corresponding nerve, and gives 

 branches which supply the sheaths of the tendons and the joints, some of them 

 anastomosing across the front of the bones with similar branches from the opposite 

 side. At about the middle of the last phalanx, the two arteries of each finger 

 converge and form an arch, from which numerous branches proceed to supply the 

 skin and subcutaneous tissue of the tip of the finger. Other offsets pass to the 



Fig. 365. SUPERFICIAL DISSECTION OP THE LOWER PART OF THE 



FOREARM AND THE HAND, SHOWING THE RADIAL AND ULNAR 

 ARTERIES, THE SUPERFICIAL PALMAR ARCH, AND THE ACCOM- 

 PANYING NERVES. (R. Quain.) 



a, on the deep fascia of the forearm, between the tendons of 

 the palmaris longus and flexor carpi radialis muscles ; b, points by 

 a line crossing the pisiform bone to the ulnar nerve ; c, points 

 to the styloid process of the radius and twigs of the radial nerve ; 

 1, radial artery lying on the flexor longus pollicis ; 1', the same 

 passing beneath the tendons of the ext. ossis metacarpi and ext. 

 brevis pollicis ; 2, superficial volar branch, piercing the short 

 muscles of the thumb and emerging below to join the superficial 

 palmar arch ; 3, external branch of the princeps pollicis ; 4, radialis 

 indicis ; a branch from the superficial arch is seen joining the 

 internal branch of the princeps pollicis ; 5, ulnar artery lying upon 

 the flexor profundus digitorum ; 5', the same descending on the 

 anterior annular ligament to form the superficial palmar arch ; 6, 

 deep branch of the ulnar artery passing between the abductor and 

 flexor minimi digiti to join the deep arch, accompanied by the deep 

 branch of the ulnar nerve ; 7, 8, 9, 10, digital arteries from the 

 superficial arch ; 7, and 8, are accompanied by the digital branches 

 of the ulnar nerve, and 3, 4, 9, and 10, by branches of the median 



structures on the back of the second and third pha- 

 langes, and form a close plexus beneath the matrix of 

 the nail. 



The varieties observed in the branches of the superficial 

 palmar arch will be noticed after the description of the deep 

 arteries of the hand. 



THE DEEP BRANCH OF THE ULNAR ARTERY arises 



at the commencement of the superficial palmar arch, 



immediately below the pisiform bone ; passing deeply into the palm between the 

 abductor and short flexor muscles of the little finger, it inosculates with the 

 termination of the radial artery, and so completes the deep palmar arch. 



RADIAL AETEEY (IV). 



The radial artery appears by its direction to be the continuation of the brachial, 

 although it does not equal the ulnar in size. It extends along the front of the 

 forearm as far as the lower end of the radius, below which it turns round the outer 

 border of the wrist, and descends to the upper end of the space between the ineta- 

 carpal bones of the thumb and fore finger : there it passes forwards into the palm 

 of the hand, supplies digital branches to the thumb and index finger, and terminates 

 in the deep palmar arch. In consequence of the changes in its direction, the course, 

 relations and branches of the radial artery may be separately described in the 

 forearm, at the wrist and in the hand. 



IN THE FOREARM. The radial artery, commencing at the point of bifurcation 



