ANTERIOR HUMERAL REGION. 



233 



Fig. 96. 



3 ,. 



fiorder is thin and tendinous above, where it is connected with the 

 aponeurotic covering of the infra-spinatus muscle, and thick below. 



Actions. The deltoid is the elevator muscle of the arm in a direct 

 line, and by means of its extensive origin can carry the arm forwards 

 or backwards so as to range with the hand a considerable segment of 

 a large circle. The arm, raised by the deltoid, is a good illustration 

 of a lever of the third power, so 

 common in the animal machine, by 

 which velocity is gained at the ex- 

 pense of power. In this lever, the 

 weight (hand) is at one extremity, 

 the fulcrum (the glenoid cavity) at 

 the opposite end, and the power 

 (the insertion of the muscle) be- 

 tween the two, but nearer to the 

 fulcrum than to the weight. 



Anterior Humeral Region. 



Coraco-brachialis, 

 Biceps, 

 Brachialis anticus. 



Dissection. These muscles are 

 exposed, on the removal of the 

 integument and fascia from the an- 

 terior half of the upper arm, and 

 the clearing away of the cellular 

 tissue. 



The CORACO-BRACHIALIS, a name 

 composed of its points of origin and 

 insertion, arises from the coracoid 

 process in common with the short 

 head of the biceps ; and is inserted 

 into a rough line on the inner side 

 of the middle of the humerus. 



Relations. By its anterior sur- 

 face with the deltoid, and pectoralis 

 major. By its posterior surface 

 with the shoulder-joint, the humerus, subscapularis, teres major, latis- 

 simus dorsi, short head of the triceps, and anterior circumflex vessels. 



* The muscles of the anterior aspect of the upper arm. 1 . The coracoid 

 process of the scapula. 2. The coraco-clavicular ligament (trapezoid), passing 

 upwards to the scapular end of the clavicle. 3. The coraco-acromial ligament, 

 passing outwards to the acromion. 4. The subscapularis muscle. 5. The 

 teres major ; the triangular space above this muscle is that through which the 

 dorsalis scapulae vessels pass. 6. The coraco-brachialis. 7. The biceps. 8. 

 The upper end of the radius. 9. The brachialis anticus ; a portion of the mus- 

 cle is seen on the outer side of the tendon of the biceps. 10. The internal head 

 of the triceps. 



