. FASCIA AND MUSCLES OF THE ARM. 317 
Muscles. Nerves. Origin. 
Pee ; } Cireumflex | 
eres minor 
Tene | Suprascapular Ch5o6 
nfraspinatus 
Teres major | Lower subscapular 
Subscapularis Lower and upper subscapular 
ee en = — es = = SE ne — | 
ACTIONS. 
The principal action of this group of muscles is on the shoulder joint. They have also 
secondary actions in relation to movements of the trunk and lmbs. 
1. Movements at the Shoulder Joint. 
a. Abduction. Adduction. 6. Flexion (Forwards). Extension (Backwards). 
_ Deltoid Teres major Deltoid (anterior fibres) Deltoid (posterior fibres) 
Supraspinatus | Teres minor | Subscapularis Teres major 
| Pectoralis major Pectoralis major Infraspinatus 
Latissimus dorsi Coraco-brachialis Latissimus dorsi 
Coraco-brachialis Biceps Triceps | 
- Biceps (short head) | 
Triceps (long head) 
| (Weight of limb) | 
c. Rotation Outwards. Rotation Inwards. 
Deltoid (posterior fibres) | Deltoid (anterior fibres) 
Infraspinatus Teres major 
Teres minor Pectoralis major 
Latissimus dorsi 
d. Circumduction—combination of previous muscles. 
The various movements at the shoulder joint are greatly aided by the muscles acting on the 
shoulder girdle. In raising the arm above the head, for instance, the humerus is brought to the 
horizontal position by the deltoid and supraspinatus, and the movement is continued by the 
elevators of the shoulder girdle. . Again, in forward and backward movements at the shoulder 
joint, great assistance is derived from muscles acting directly on the shoulder girdle—pectoralis 
minor and serratus magnus ; trapezius and rhomboidei. 
2. In relation to the trunk and limbs, the shoulder muscles, by fixing the humerus, have 
auxiliary power on the one hand in movements of the trunk, such as forced inspiration ; on the 
other hand, acting along with muscles fixing the elbow joint, they stiffen the limb so as to 
permit of the more refined movements of the wrist and fingers. 
FASCIA AND MUSCLES OF THE ARM. 
FASCIA. 
The superficial fascia presents no features of importance. There is a bursa 
beneath it over the olecranon process, and occasionally another over the inner 
condyle of the humerus. 
The deep fascia forms a strong tubular investment for the muscles on the front 
and back of the humerus. It is continuous above with the deep fascia of the 
shoulder and axilla, and is further strengthened by fibres derived from the inser- 
tions of muscles attached to the upper part of the humerus. At the elbow it 
becomes continuous with the deep fascia of the forearm, and gains attachment to 
the condyles of the humerus and the olecranon process of the ulna ; it is strength- 
_ ened also by important bands associated with the insertions of the biceps in front 
and the triceps behind. 
