CHAP, xiii.] DOUBLE-HAND. 333 



to have clearly represented the trapezoid of the left hand, bearing an 

 index finger. The metacarpals and phalanges needed no description. 



The muscles are described in detail [9. v.]. Some of the features 

 in the distribution of the arteries and nerves are of interest, and I 

 transcribe Dwight's account in full. It appears that, like the bones, 

 the vessels and nerves proper to the radial side of a normal left arm 

 have in a measure been transformed into parts proper to the ulnar side 

 of a right arm. 



"The Arteries. The brachial divides at about the junction of the 

 middle and lower thirds of the humerus. The. main continuation, which 

 is the ulnar proper, runs deeply under the band thought to represent 

 the pronator radii teres, to the deep part of the fore-arm where it gives 

 off the interosseous. Above the elbow there is a branch runnina: 

 backward between the internal condyle and the olecranon. The inter- 

 osseous branches are not easy to trace. There seems to be an anterior 

 interosseous and three branches on the back of the forearm, one running 

 on the membrane and one along each bone. At least two of them share 

 in a network on the back of the carpus. Having reached the hand the 

 ulnar artery runs obliquely across the palm to the cleft between the 

 two sets of fingers, supplying the four normal fingers and the nearer side 

 of the extra middle finger. The other branch of the brachial crosses 

 the median nerve and runs, apparently superficially, to the outer side 

 of the fore-arm. It supplies the little and ring fingers and the corre- 

 sponding side of the middle finger of the supernumerary set. There is 

 no anastomosis in the palm between the superficial branches of the 

 two arteries. Each gives off a deep branch at the usual place, which 

 forms a deep palmar arch from which some interosseous arteries spring. 

 There is also an arterial network over the front of the carpal bones. 

 The arteries of the deep parts of the hand cannot all be seen. 



The Nerves. The ulnar nerve proper pursues a normal course and 

 supplies the palmar aspect of the little finger and half the ring finger of 

 the normal hand. Near the wrist it gives off a very small posterior 

 branch, which is not well preserved, but which seems to have had less 

 than the usual distribution. The median nerve is normal as far as the 

 elbow, running to the inner side of the extra condyle. It is then lost 

 in the dried fibers of the flexor sublimis, from which it emerges in two 

 main divisions near the middle of the fore-arm. The inner of these soon 

 divides into two, of which one supplies the adjacent sides of the ring 

 and middle fingers and the other those of the middle and index fingers 

 of the normal hand. The outer division of the median supplies the 

 outer side of the index and both sides of the extra middle finger and 

 one side of the extra ring finger. One of the branches to the index 

 gives off a dorsal branch, and there is a doubtful one for the extra 

 middle finger. The musculo-spiral nerve passes behind the humerus as 

 usual. A nerve which is undoubtedly continuous with it emerges from 

 the hardened muscles over the fused outer condyles. It seems to be the 

 radial branch changed into an ulnar. It runs with the extra ulnar 

 artery to the hand and sending a deep branch into the palm, goes to 

 the ring finger. There is a detached branch on the other side of the 

 little finger which in all probability came from it. The deep branch 

 sends a twig along the metacarpal bone of the ring finger. It probably 



