BEANCHES OF THE MUSCULO-SPIEAL NERVE. 



593 



(i) The external cutaneous branches, two in number, arise where the nerve 

 pierces the external inteiinuscular septum. 



The iippcr hranch, the smaller of the two, is directed downwards to the fore 

 part of the elbow, along the cephalic vein, and distributes filaments to the lower 

 half of the upper arm on the anterior aspect. The loivcr branch extends as far 

 as the wrist, distributing offsets to the lower half of the arm, and to the fore- 

 aim, on their posterior aspect, and is connected near the ^vrist with a branch of 

 tiie external cutaneous nerve. 



FiK. 363. 



Fi-. 



563. — Dorsal Cutaneous Nerves 

 OF THE Hand. ^ 



The distribution delineated in this 

 figure is not the most common, there being 

 a larger than usual branch of the \ilnar 

 nerve : 1, the radial nerve descending 

 beside the principal radial cutaneous vein ; 

 2 ami 3, dorsal branches to the two sides 

 of the thumb ; 4, branch to the radial 

 side of the forefinger ; 5, branch to the 

 forefinger and middle finger, communi- 

 cating with one from the ulnar neive ; 



6, the posterior branch of the ulnar nerve ; 



7, communicating twig ; 8, collateral 

 branch to the middle and ring fingers ; 

 9, collateral branch to the ring and little 

 fingers ; 10, branch to the inner side of 

 the hand and little finger. 



Kadial nerve. — Tlie radial 

 nerve, continuing straight down 

 from the musculo-spiral, is con- 

 cealed by the long supinator mus- 

 cle, and lies a little to the outer 

 side of the radial artery. This 

 position beneath the supinator is 

 retained to about three inches 

 from the lovrer end of the radius, 

 where the nerve turns backwards 

 beneath the tendon of the muscle, 

 and becomes subcutaneous. It 

 then separates into two branches, 

 which ramify in the integument 



on the dorsal aspect of the thumb and the next two finders in 

 lowing manner- 



(«) The external branch extends to the radial side of the thumb, and is joined 

 by an offset of the external cutaneous nerve. It distributes filaments over the 

 ball of the thumb. 



(5) The internal jwrtlon communicates with a branch of the external cuta- 

 neous nerve on the back of the forearm, and divides into digital branches ; o7ie 

 running along the ulnar side of the thumb, a second on the radial side of the 

 index finger, a third dividing to supply the adjacent sides of the index and 

 middle fingers, while ^fourth joins with an offset from the dorsal branch of the 

 ulnar, and along with it forms a branch for the supply of the contiguous sides of 

 the middle and ring fingers. These branches communicate on the sides of the 

 fingers with the palmar digital nerves. 



Sometimes the interspace between the middle and ring fingers is entirely sup- 

 plied by the radial, and at other times entirely by the ulnar neiTe. 



VOL. I. . Q Q 



the fol- 



