1894.] ANATOMY OF ORNITHOEHYNCHUS. 711 



hand, and gives off a branch to the sup. longus and extensor 

 carpi radialis longior. The lower trunk, formed by the seventh 

 and eighth cervical, first dorsal, and a filament from second dorsal, 

 is much the larger of the two. This trunk divides into three 

 terminal branches about the middle of the arm : — (a) One passes 

 downwards, enters forearm, and is distributed to the cleft between 

 the index and middle fingers on palmar aspect ; (/3) The next, also 

 a cutaneous branch, is about the same size as the first ; it is 

 distributed to the third and fourth clefts. The above two nerves 

 would seem to represent superficial portion of median and part of 

 ulna, (y) The third branch of the lower trunk, the largest of the 

 three, passiDg down arm, gives off two branches to the triceps, 

 which curve round the lower border of latissimus dorsi. One of 

 these is the posterior interosseous, which passes through triceps, 

 winds round humerus something like the musculo-spiral of 

 human anatomy. This nerve next passes between brachialis 

 anticus and muscles arising from the radial condyle of humerus, 

 and, passing into forearm, perforates the supinator brevis and 

 supplies the usual muscles on the back of the forearm, with the 

 exception of extensor carpi radialis brevior, extensor primi and 

 secundi inter-nodii pollicis, all of which muscles are absent. 



The continuation of the third branch passes into forearm, beneath 

 the anconeus internus, and, after supplying the muscle, gives off 

 branches to the flexor cai'pi ulnaris and the ulnar portion of 

 the flexor sublimis digitorum ; it then continues its course down 

 forearm and ends by supplying the ulnar side of the fifth digit. 

 It communicates in the forearm with the branch to the fourth 

 cleft. 



Other branches from lower part of plexus : — The seventh nerve 

 gives off a branch to latissimus dorsi before it joins the plexus. 

 From the lower part of plexus a branch is given to the pectoralis 

 major. The median nerve arises by two roots, and, after supplying 

 the biceps, coraco-brachialis, and brachialis anticus, passes through 

 supracondyloid foramen into the forearm. 



Lumbar Plexus. 



Obturator nerve. — Its chief origin is from the sixteenth dorsal 

 nerve, allowing two lumbar vertebra?. The nerve passes out 

 between the sixteenth and seventeenth dorsal vertebra?. It is 

 joined by a slender branch from the seventeenth dorsal, a 

 subcostal nerve. The nerve passes along pelvis in the usual 

 position and supplies the usual muscles, together with a slender 

 branch to the semi-mem branosus. It also gives off a branch in the 

 abdomen, which, after dividing into several branches, passes to 

 psoas and iliacus. 



The anterior crural nerve arises by two fairly large branches 

 from the seventeenth dorsal and the first lumbar nerves. The rest 

 of the first lumbar together with the whole of the second pass 

 into the pelvis, forming the luni bo- sacral cord. 



