ANATOMY IN A NUTSHELL. 115 



Insertion. — Into the radial side of the first phalanx of ring finger. 

 Third palmar interosseous. 



Origin. — By one head from the radial side of the fifth metacarpal bone. 

 Insertion. — Into the radial side of the first phalanx of little finger. 

 Each finger has two [nterossei muscles except the little finger. The Ab- 

 ductor minimi digiti takes the place of one of the pair. 

 Nerve Supply. — Ulnar. 

 Blood Supply. — Deep palmar arch. 

 Action. — Same as the Dorsal interossei,bu1 these adduct instead of abduct. 



LKSSOX XXX. 



Fascia of the arm. — Just beneath the skin is the superficial fascia which 

 has two layers, a superficial one consisting mainly of adipose tissue, and a deep 

 one which is fibrous in structure and is in contact with the deep fascia. The 

 superficial nerves; vessels and lymphatics lie between these two layers. 



The deep fascia of the arm forms a sleeve which encloses the muscles and 

 most of the vessels and nerves. It is continuous with the fascia of the chest. 

 back, shoulder above by being attached to the clavicle, the scapula ami the 

 spine, and to that of the forearm by being attached to the condyles of the hu- 

 merus and olecranon of the ulna. It is thin over the Biceps, thick over the 

 Triceps; strengthened on the inner side by fibers from the tendon of the Pec- 

 toralis major and Latissimus dorsi, on the outer side by fiber- from the tendon 

 of the Deltoid; the axillary fascia is also continuous with it. The external in- 

 termuscular septum extending from the insertion of the Deltoid to the External 

 condyle and attached to the superior condylar ridge joins the inner surface of 

 the deep fascia, thus dividing the sleeve or cylinder of fascia into an anterior 

 and posterior compartment, the anterior one having flexor muscles in it and the 

 the posterior one extensor muscle.-. This septum is pierced by the musculo- 

 spiral nerve and superior profunda artery from behind forward. It has five 

 muscles attached to it, viz.. Deltoid, Brachialis anticus, Triceps. Supinator 

 longus, and Extensor carpi radialis longior. In these five muscles if we sub- 

 stitute the Deltoid for Anconeus we will have the five muscles supplied by the 

 musculo-spiral nerve. 



The internal intermuscular septum i- thicker than the external one: it 

 extends from the insertion of the Coraco-brachialis to the internal condyle ^\ 

 the humerus, being attached to the supracondylar ridge to the inner surface of 

 the sleeve of fascia of the forearm. It also divides the muscles into an anterior 

 and posterior division. Il has three muscles attached to ii. vi/... the Triceps, 

 Brachialis anticus, and Coraco-brachialis, and occasionally the Pronator radii 

 teres. If we stubsitute the Triceps for Biceps in this group of muscles we will 

 have the muscles supplied by the niusculo-cutaneotis nerve. The basilic vein 

 pierces the deep fascia at the junction n\' the lower third with the middle third 

 of the humerus. 



The deep fascia of the forearm is continuous with thai of the arm at the 

 elbow and with that of the hand ;it the wrist. It passes over the anterior an- 



