330 HEALTH AND DISEASE 



Humeralis Externus. — This is a long fleshy muscle partly encircling 

 the upper arm. 



Origin. — It arises from the jjosterior part of the head of the humerus, 

 and winds round the outer side of the bone in the furrow of torsion. 



Insertion. — After crossing the elbow-joint, it becomes inserted partly 

 into the inner side of the head of the radius and partly also into the ulna. 



Action. — To flex the fore-arm on the humerus and rotate it outwards. 



Scapulo-Ulnaris. — A broad, thin mu.scle extending from the scapula 

 to the elbow, on the inner aspect of the arm. 



Origin. — By a broad, thin aponeurotic tendon from the posterior border 

 of the scapula. 



Insertion. — Into the superior and posterior part of the olecranon or 

 elbow and into the fascia of the arm. 



Action. — To extend the lower on the upper arm, and to tighten the 

 fascia of the fore-arm to give the muscles support. 



Triceps Extensor Cubiti. — This is the largest muscle of the fore 

 extremity. 



It fills in the triangular space between the hinder edge of the shoulder 

 and the point of the elbow. It is made up of three portions or heads, dis- 

 tinguished as the caput magnum or large head, the caput parvum or small 

 head, and the caput medium or intermediate. 



The caput magnum or large head arises from the posterior border of the 

 scapula as high as the dorsal angle, and the caput medium arises from the 

 upper and outer part of the humerus. The caput parvum arises from the 

 inner face of the same l)one. 



Insertion. — All three divisions are inserted into the point of the elbow. 

 A synovial bursa is interposed between the tendon of the caput magnuiu 

 and the bone. 



Action. — To extend the fore-arm on the humerus. 



Anconeus. — A small fleshy muscle situated in the angle between the 

 elbow and the arm. 



Origin.— ¥vo\\\ the lower extremity of the humerus behind. 



Insertion. — Into the anterior and outer part of the ulna. 



Action. — To assist in extending the lower on the upper arm. 



Flexor Metacarpi Internus (Internal Flexor of the Metacarpus or 

 canon). — This muscle lies on the inner and back part of the radius or fore- 

 arm, with which it is in contact. 



Origin. — From the inner surface of the internal condyle of the humerus 

 or upper-arm bone. 



Insertio7i. — The tendon of insertion commencing some distance above 

 the knee passes over a groove on the lower extremity of the radius, and 



