ANATOMY IN A NUTSHELL. 79 



to the back of the forearm between the radius and ulna above this membrane. 



The inferior radio-ulnar articulation is a trochoides, and is formed by the 

 head of the ulna and the sigmoid cavity of the raidus and fibro-cartilage. Its 

 ligaments are the anterior and posterior radio-ulnar which make the capsular 

 ligament. The anterior radio-ulnar ligament passes from the front border of 

 the sigmoid cavity of the radius to the anterior surface of the head of the ulna. 

 The posterior one is a similar ligament on the posterior surface. The triangular 

 interartieular fibro-cartilage is at the lower end of the ulna, between the styloid 

 process and the radius. Its perimeter is attached to the ligaments of the wrist; 

 it is attached by its apex to the depression between the head and styloid pro- 

 cess of the ulna, by its base to the lower end of the radius. Sometimes it is 

 perforated, in such a case the synovial membrane communicates with that of 

 the wrist. 



The blood supply is the anterior interosseous and anterior carpal arch. 



The nerve supply is the anterior and posterior interosseous. Synovial 

 membrane, the membrana sacciformis, lines the adjacent surfaces of the ulna 

 and the interartieular fibro-cartilage. and the ulna and the radius. As stated 

 before, it sometimes communicates with the wrist-joint. 



j Brachialis amicus. — Description. — (Plate XVI.) — This is a broad muscle 

 which covers the elbow-joint and the lower half of the front of the humerus. 

 It is somewhat compressed from before backward and is broader in the middle 

 than at either extremity. Its fibers converge to a thick tendon. The outer 

 border of the muscle is in relation with the musculo-spiral nerve and radial re- 

 current artery. 



Origin. — (1) Lower half of outer and inner surfaces of shaft of humerus; 

 (2) intermuscular septa; (3) commences above at insertion of Deltoid and ex- 

 tends below to within one inch of margin of articular surface. (Plate XXIII.) 



Insertion. — Into a rough depression on the anterior surface of the coron- 

 noid process of the ulna, being received into an interval between two fleshy 

 slips of the Flexor profundus digitorum, (Plate XXV.) 



Action. — Flexor of forearm. 



Nerve Supply. — Fifth and sixth cervical through the musculo-cutaneous 

 and musculo-spiral. 



Blood Si pply.- Brachial artery. 



Subanconeus. Description.- The Subanconeus is a name given to a few 

 fibers from the under surface of the lower pai I of the Triceps muscle. By some 

 authors it is regarded as the analogue of the Stfbcrureus in the lower limb, but 

 it is not a separate muscle. 



Origin. — Humerus above olecranon fossa. 



Insertion. Posterior ligament of elbow-joint. 



A< tion. 1 >raws up posterior ligamenl during extension of forearm. 



Nerve Supply. —Musculo-spiral. 



Blood Supply. Brachial artery. 



Pronator radii teres. Description. (Plate KXIX.) This muscle 

 arises by two heads, beiween which the median nerve enters the forearm. 

 It passes obliquely across the forearm from the inner to the outer side, and ter- 



