482 THO.MAS DWIGHT ON THE 



head sending a small slip to the Itase of the little finger. No such muscle has been 

 preserved on the normal side. The common extensors of the fingers maj- be described 

 as follows : A fleshly mass arises from the outer side of the normal olecranon, 

 between it and the fused outer condyles, which sends extensor tendons to the four 

 normal fingers. The one to the index is very small and soon separates from the 

 othei's. Theie are the usual cross connections over the metacarpus l)et\veen 

 the tendons of the innei- three fingers. An extensor jii'ojvlus indicia arises from the 

 middle of the ulna and the intero.s.seous membrane. The extensor of the extra hand 

 arises partly in couunon with the other from the fused outer condyles and partly 

 from the region of tlu' inverted olecranmi. It sends tendons, more or less fused, to 

 the three extra iligits and a small slip to the index of the normal hand which joins 

 near its insertion the tendon of the extensor jjrojjrlus Indicls already mentioned. 

 There arises also from the l^ack of the inverted ulna and perhaps from the inter- 

 osseous meml.)rane a second extensor proprlus Indlcis which is very much the largest 

 of the four extensor tendons going to that finger. The next largest is the extensor 

 proprhis of the normal hand. There arises also from the l)aclv of the inverted ulna 

 near the wrist another small muscle with a tendon going to the back of the mid- 

 dle finger of the extra hand. Near this, f)ut still lower, was another small muscle, the 

 tendon of which had l>een cut near the base of the metacarpus. 



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 running back- 

 ward between the internal condyle and the olecranon. The interosseous branches are not 

 easy to trace. There seems to he an anterior interosseous and three branches on the back 

 of the for^^arm, one running on the membrane and one along each bone. At least two of 

 these share in a network on the ])ack of the carpus. Having I'eached the hand the ulnar 

 artery runs obliquely across the palm to the cleft between the two sets of fingers, sup- 

 plying the four normal fingers and the nearer side of the extra middle finger. (Plate 44 

 fig. 5.) The other branch of the l)rachial crosses the median nerve and runs, apparently 

 superficially, to the outer siile of the forearm. It supplies the little and ring fingers and 

 the corresponding side of the middle finger of the supernumerary set. There is no 

 anastomosis in the palm between the superficial l)ranches of the two arteries. Each gives 

 off a dee}) 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 jiarts of the hand cannot all be seen. 



The Nerves. The ulnar nerve proper, pursues a normal course and supplies the 

 palmar aspect of the littli' linger and half the ring finger of the normal hand. Near the 



