544 Proceedings of the Royal Irish Academy. 



bone of first pollex ; the other, into the base of the terminal bone of 

 same (ext. intemod pol. primi). 



Ext. prim, intemod. pol.: — Origin noiTQal; insertion into base of 

 second phalanx of second pollex. An aponeurosis fi'oni the tendon of 

 last, and fi'om the bone close to its insertion, passed this tendon, to the 

 majority of the fibres passing over it. 



Ext. secnndi int. pol.: — Origin and course normal; joined "with 

 tendon of last muscle to form a common tendon, ■which diyided at the 

 cleft between second and third pollex. The portion corresponding to this- 

 muscle diyided at head of first phalanx of thiixl pollex into thi'ee slips :: 

 the middle passed over the joint, and was inserted into base of terminal 

 phalanx ; the two lateral were inserted into the base of second phalanx. 

 This is the reverse of the arrangement with ordinary dorsal digital 

 aponeurosis, and approximates to the fiexor ari'angement of tendon. 



Ext. indicis : — Origin normal, but prolonged up as far as the at- 

 tachment of the supinator brevis ; course normal ; insertion nonnal ; 

 tendon joined by small slip fi'om ext. com. dig. 



The Muscles of the Left Hand : — Posterior surface : supinat. long, 

 and extensors of the carpus, normal. 



Extensor com. digitorum : — Divided into two tendons only, which 

 went to the middle and ring fingers ; no trace of a tendon to the index 

 or little finger. 



Extensor ossis met. pol. : — Origin normal; divided into three slips : 

 first, inserted into base of metacai-pal bone of first pollex (ext. oss, 

 met. pol. prim.); second, into cartilaginous nodule, at apex of first 

 pollex, which is the homologue of the terminal bone of first pollex on 

 right hand (ext. interned, pol. prim.); third, into an aponeurosis on 

 the back of the fii'st phalanx of second pollex, which was formed bj^ 

 the tendon of this and three other muscles (ext. primi internod. pol. 

 secund.) Between the two tendons last mentioned a web of dense 

 fascia extended, which was closely connected with both, and resembled 

 the structure described in the right hand. The concave margin con- 

 stituted the arch into which were inserted some of the short muscles, 

 of the anterior group. 



Ext. primi internod. pol. : — Origin normal ; insertion into the 

 same aponeurosis as last. 



Ext. sec. internod. pol. : — Origin normal, divided into two tendons ; 

 the external much the larger, inserted together into the same aponeu- 

 rosis as last two muscles. This aponeurosis, formed by union of the 

 four tendons, expanded towards the head of the first phalanx, and 

 formed a cap which enclosed it, and was inserted into the base of the 

 second phalanx. 



Ext. indicis : — Origin normal ; insertion nonnal. It received no- 

 slip from ext. digit, communis. 



The Arteries of Eight Hand : — The ulnar artery gave off a poste- 

 rior carpal and a communicating branch, and then passed across the 

 palm to the radial side of second pollex, along which it continued as its- 

 external digital artery. The supei-ficial palmar arch was completed 



