lit) ANATOMY IN A NUTSHELL. 



nular ligament which is in reality the aponeurosis which separates the first and 

 second layers of the muscles of the forearm. It passes from the pisiform bone 

 and unciform process to the scaphoid and trapezium; it is a strong fibrous band. 

 At the posterior aspect it is thickest where it is attached to the sides of the 

 triangluar posterior surface of the olecranon and to all of the posterior ridge of 

 the ulna. It receives a band from the bicipital fascia below the internal con- 

 dyle in front, and an aponeurosis from the insertion of the Triceps behind. It 

 is pierced by a communicating vein at the cubital fossa. 



The posterior annular ligament is strengthened by transverse fibers and 

 passes from the outer border of the lower end of the radius across to the inner 

 side of the pisiform and cuneiform bones, its inner surface being attached to the 

 ridge on the posterior surface of the radius. It makes six canals for the passage 

 (if the extensor tendons; the first canal has the Extensor ossis metacarpi pol- 

 licis and Extensor brevis pollicis; the second the Extensor carpi radialis longior 

 and Extensor carpi radialis brevior; the third the Extensor longus pollicis; the 

 fourth the Extensor communis digitorum, which is in the superficial layer, 

 and the Extensor indicis, which is in the deep layer; the fifth, the Extensor 

 minimi digiti which is in the superficial layer; the sixth, the Extensor carpi 

 ulnaris which, is in the superficial layer. 



The anterior annular ligament has nine muscles attached to it, all those of 

 the thumb except the Adductor transv< rsus pollicis, and all those of the little 

 finger except the Abductor minimi digiti; then there are four of the thumb 

 and two of the little finger, making six ; besides these six it has the Flexor carpi 

 ulnaris, Palmaris longus, and Palmaris brevis, making the nine. The tendon of 

 i he Flexor carpi radialis pierces the anterior annular ligament and the Palmaris 

 Longus passes over it. but is also attached to it. The median nerve and the 

 tendon- of three muscles pass under it; the muscles are the Flexor sublimis 

 digitorum, flexor profundus digitorum, and Flexor longus pollicis. 



Fascia of the hand. — The fascia on the back of thehand isthinand is com- 

 posed mostly of transverse fibers. This fascia is a continuation of the posterior 

 annular ligament. It connects the extensor tendons together on the back of the 

 hand. Between the fingers it dips down to join the web which connects 

 the bases of the fingers. The deep layer is attached to the back of the meta- 

 carpal.- and covers the Dorsal intemssei. 



Palmar Fascia. The deep palmar fascia consists of strong fibrous tissue 

 covering the palmar surface of the hand. It is for the most part formed by the 

 expansion of the tendons of the Palmaris longus. It is also continuous with 

 the anterior annular ligamenl proximally. It has a central and two lateral 

 portions. The central portion is triangular with the apex towards the wrist 

 and base towards the fingers. The superficial part is formed by longitudinal 

 filier- and the deep part bytransverse fibers. Its base is divided into four pro- 

 cesses wh'n h j< in the ligamenta vaginalis of the finger tendons. (Plates XXIX- 

 XX XI o 



Ligamenta vaginalis are fibrous -heaths or theca over the flexor tendons. 

 They are so attached to the phalanges as to form osseo-aponeurotic canals 

 These -heaths are strong opposite the middle of the first and second phalanges, 



