OF THE MUSCLES. 



101 



it sends off an auxiliary tendon to the extensor raetacarpi 

 magnus. Action. To draw the scapula forward ; and through 

 its auxihary tendon to raise the fore arm. 



The muscles of the arm, which remain to be dissected, 

 are characterized by having fleshy belhes, terminating in 

 long tendons ; most of them having distinct fascial sheaths ; 

 all the more important originating from the lower head 

 of the humerus. They are divided into extensors and 

 flexors : four extensors and seven flexors. An eighth 

 flexor, answering to the pronator teres, has been described 

 by Dr. Knox of Edinburgh ; but, never having been able 

 to find that muscle, I conclude it is sometimes encountered, 

 yet is not invariably present. 



FIGS. 



DEEPEST-SEATED MUSCLES AT 

 THE BACK OF THE HUMERUS. 



1, The scapulo-humeralis major. 



2, Humeral is. 



3, Anconeus. 



Extensor metacarpi magnus {Plate III. 0. 16). Origin. 

 From the ridge extending from the outer condyle of the 

 humerus, by tendon, which is likewise common to the ex- 

 tensor pedis. Insertion. To the anterior of the upper head 

 of the cannon bone, by strong tendon. 



