chap, xv.j THE WRIST AND HAND. 249 



joint. The other sheaths reach above to the upper 

 border of the annular ligament, that for the two 

 radial extensors, however, beginning about half an 

 inch above the ligament. The sheaths for the extensor y 

 communis and the extensor minimi digiti extend below 

 to the middle of the metacarpus. That for the 

 extensor indicis barely reaches the metacarpus. The 

 other sheaths follow the tendons to their insertions. 



Blood-vessels and lymphatics. The hand 

 is very well supplied with blood, and indeed the finger 

 pulp is one of the most vascular parts in the body. 

 Cases are recorded where the tip of the finger has been 

 accidentally cut off, and has grown again to the limb 

 on being immediately re-applied. The position of the 

 palmar arches has been pointed out. Wounds of these 

 arches, and indeed of most of the arteries of the palm 

 and wrist, are serious, on account of the difficulty of 

 reaching the bleeding point without seriously damaging 

 important structures, and on account of the free anas- 

 tomoses that exist between the vessels of the part. 

 The deep palmar arch may be wounded by a pene- 

 trating wound from the dorsum, and indeed Delorme 

 has pointed out that this arch may be ligatured 

 from the dorsum after a preliminary resection of 

 the upper part of the third metacarpal bone. It is 

 well known that hsemorrhage from either of the 

 palmar arches cannot be checked by ligature of the 

 radial or ulnar artery alone, on account of the connec- 

 tion of the arches with those vessels ; and it is also 

 known that simultaneous ligation of the two vessels 

 may have no better effect, owing to the anastomoses 

 between the palmar arches and the interosseous 

 vessels. The anastomosis is carried on by means of 

 the carpal arches. The anterior carpal arch communi- 

 cates with the anterior interosseous artery above, and 

 with the deep palmar arch, by the recurrent vessels 

 below. The posterior carpal arch communicates with 



