708 MR. F, G. PARSONS ON THE [June 16, 
of the atlas from which communicating branches are given off. 
From the 3rd cervical a single large nerve passes to the auricle 
and occiput, which evidently corresponds to the small occipital and 
great auricular. From the 3rd also come two superficial cervical 
nerves, which supply the skin over the auterior and _ posterior 
triangles of the neck respectively. The 4th cervical nerve com- 
municates with the upper part of the 5th, and from the junction 
come off descending cutaneous branches to the skin of the arm 
and shoulder. From the deep part of the plexus branches are 
given off to the surrounding muscles, a small communicating 
spinal accessory coming from the 4th. 
The arrangement of the Brachial Plexus corresponds very closely 
with that of Man; it is chiefly remarkable for the fact that the 
subscapularis is supplied by three separate twigs, one of which is 
derived from the suprascapular nerve and the other two from the 
posterior cord. There is no distinct musculo-cutaneous nerve, the 
coraco-brachialis, biceps, and brachialis anticus being supplied by 
the outer head of the median. The suprascapular comes off after 
the junction of the 5th and 6th cervicals. The external anterior 
thoracic is given off from the outer cord after the junction of the 
7th cervical, but has no communication with the internal anterior 
thoracic. The outer head of the median is, as in Man, derived 
from the 5th, 6th, and 7th; it is not joimed by the inner head, 
which comes from the 8th cervical and 1st dorsal, until it reaches 
the middle of the arm. ‘The trunk formed by the union of the 
two heads passes through the supracondylar foramen and just 
below the elbow divides into two branches, the outer of which 
corresponds in its distribution to the human radial nerve, that is 
to say it supplies the three and a half outer fingers on their dorsal 
surfaces ; in its course down the forearm it lies superticial to all 
the muscles. The inner of the two branches gives off twigs to the 
tlexor muscles of the forearm and accompanies the median artery 
to the hand, passing deep to the pronator radii teres, palmaris 
longus, and flexor carpi radialis. In the hand it supplies the 
thenar muscles as well as the skin of the outer three and a half 
fingers on their palmar surfaces. There is no distinct anterior 
interosseous branch. 
The ulnar nerve separates from the inner head of the median 
just above the middle of the arm; it at once gives off two internal 
cutaneous branches for the inner side of the forearm and then > 
passes deep to the epitrochleo-anconeus, which it supplies. Im- 
mediately after this it gives off a branch to the flexor carpi ulnaris, 
but none to the flexor profundus digitorum, and passes down the 
forearm under cover of the flexor carpi ulnaris to the radial side 
of the pisiform bone, giving off, at the junction of the middle and 
lower thirds of the forearm, a dorsal cutaneous branch, which 
supplies the back of the inner one and a half fingers. At the 
pisitorm the main stem of the ulnar divides into. superficial and 
deep branches, the former supplying the skin of the ulnar one and 
a half fingers on their palmar surfaces, the latter passing between 
