576 



HUMAN ANATOMY. 



2. Infraspinatus (Figs. 561, 572). 



Attachments. — The infraspinatus occupies the infraspinous fossa of the scapula 

 and arises from the entire extent of the fossa, with the exception of a portion 

 towards the axillary border of the bone. It also arises from the infraspinous fascia 

 which covers it. The fibres pass laterally and converge to a strong tendon, which 

 is frequently separated from the capsule of the shoulder-joint by a small bursa (bursa 



Fig. 560. 



Axillary vein 

 Axillary artery 



Brachial plexus 



Clavicle 



Subclavius 

 Costo-coracoid ligament 



Deltoid. 



Long head of biceps. 



Short head of biceps 



Insertion of 

 pectoralis major 



Pectoralis minor 



Serratus magnus 



Bicepi 



^anticus^^ .1^ m. infraspinati) and is inserted 'mlo the middle facet of 



the greater tuberosity of the humerus. 



Nerve-Supply. — By the suprascapular nerve from 

 the fifth and sixth cervical nerves. 



Action. — When the arm is hanging vertically, it is 

 the chief outward rotator of the humerus. When the 

 arm is abducted to a horizontal position, the muscle 

 draws it backward. 



Variations. — The upper portion of the muscle is sometimes 

 distinctly separated from the rest, and has been termed the 

 infraspinatus minor. On the other hand, the separation which 

 usually exists between the infraspinatus and the teres minor may 

 be entirely wanting. 



The inf^-a spinalis fascia is a strong fascia which covers 

 the infraspinatus and the teres minor, giving origin to 

 some of the fibres of both muscles. It is attached above 



to the spine of the scapula, medially to its vertebral border, and fades out laterally 



into the brachial fascia. 



ipital 

 fascia 



Dissection of thora'^ic wall and 

 anterior surface of arm. 



3. Teres Minor (Fig. 561). 



Attachments. — The teres minor arises from the upper two-thirds of the dorsal 

 surface of the scapula, close to its axillary border, and from the infraspinlbus fascia. 



