160 SPECIAL ANATOMY. 



B. Muscles of the Upper Arm. 

 a. Regio humeri anterior. 



292. 1. Biceps brachii (flexor radii). 



Position : on the anterior internal surface of the upper arm ; the 

 heads on the outer side of the axilla, betwoon pectoral, major and 

 deltoid before, latissim. dorsi and teres major behind ; the long 

 head before m. subscapular. Behind its belly : Nerv. musculo- 

 cutan., M. coraco-brachial., brachial. internus; along the internal 

 border: Art., Fv. brachiales, Nerv. medianus. Or.: 1. Caput 

 Ion gum cavit. glenoid. scapul. (at the upper edge). 2. Cap. 

 breve Proc. coracoideus (apex). Ins.: tuberositas radii; the 

 tendon is surrounded by Supinator brevis; an aponeurosis 

 passes over from it into the fascia cubiti. Use : to flex and 

 draw the fore-arm rather inwards ; stretches the fascia anti- 

 brachii. 



293. 2. Brachialis internus, flexor of the elbow. 



Pos. : behind the last muscle ; upon the inner border : 7V. Me- 

 dian., Art. brachial. , below M. pronator teres; on the outer 

 border: TV. radialis and M. supinator longus. 



Or. : Os humeri (inner surface) ; surrounding the insertion of 

 M. deltoideus. Ins. : Proc. coronoideus ulnse. 



Use : flexes the fore-arm, and draws it rather outwards. 



294. 3. Coraco-brachialis (s. perforatus Casserii). 



Pos. : above, under deltoideus, in the centre between pectoral, 

 maj. and latissim. dorsi, below at a similar elevation as the ten- 

 don of deltoideus ; covers above, Art. axillar. and brachial., Nn. 

 medianus and musculo-cut., lies below to the outer side of Art. 

 brachidlis. Or. : Proc. coracoideus (apex). Ins. : Os humeri 

 (inner border and centre) between anconxus quartus [short head 

 of triceps] and brachial. internus. Use : presses the scapula and 

 humerus towards one another ; assists in drawing the arm to the 

 chest. Antagonist to the rotators. 



Nerves: (first to third) musculo cutaneus; 



b. Regio humeri posterior. 



295. 4. Triceps (s. brac/iialis externus, s. anconseus magnus). 



Pos. : on the posterior external surface of the upper arm, sepa- 

 rated from the skin byfasc. brachialis, covers the nerv. radialis 



