466 



THE MUSCLES AND FASCIAE 



infraspinous fossa; it affords attachment, by its inner surface, to some fibres 

 of that muscle. At the point where the Infraspinatus commences to be covered 

 by the Deltoid, this fascia divides into two layers; one layer passes over the 

 Deltoid muscle, helping to form the deltoid fascia already described; the other 

 passes beneath the Deltoid to the capsule of the shoulder-joint. 



8UPRASPINATU8 TRAPEZIUS 



LEVATOR ANGULI 

 SCAPULAE 



RHOMBOIOEU8 

 MINOR 



RHOMBOIDEU8 

 MAJOR 



INFRASPINATUS 

 / ' *- TERES MINOR 



EXTERNAL HEAD 

 OF TRICEPS 



COMMON TENDON. 

 OF FLEXORS 



FLEXOR SUBU. . 



DIGITORUM 



FLEXOR PROFUNDU8 

 DIGITORUM ' 



COMMON TENDON 

 OF EXTENSORS 



ANCONEU8 

 8UPINATOR 



FIG. 351. Diagram showing attachment of muscles of shoulder and arm. Posterior aspect. 

 Origins, red; insertions, blue. 



The Infraspinatus (m. infraspinatus) is a thick, triangular muscle, which 

 occupies the chief part of the infraspinous fossa, arising by fleshy fibres from its 

 internal two-thirds, and by tendinous fibres from the ridges on its surfaces; it 

 also arises from a strong fascia which covers it externally, and separates it from the 

 Teres major and minor. The fibres converge to a tendon which glides over the 

 external border of the spine of the scapula, and, passing across the posterior part 

 of the capsular ligament of the shoulder-joint, is inserted into the middle impres- 

 _sjojj on the greater tuberosity of the humerus. The tendon of this muscle is 

 sometimes separated from the capsule of the shoulder-joint by a synovial bursa 

 (bursa m. infraspinati), which may communicate with the joint-cavit^^ 



Relations. By its superficial surface, with the Deltoid, the Trapezius, Latissimus dorsi, 

 and the integument; by its deep surface, with the scapula, from which it is separated by the supra- 

 scapular and dorsalis scapulae vessels, and with the capsular ligament of the shoulder-joint. 

 Its lower border is in contact with the Teres minor, occasionally united with it, and with the 

 Teres major. 



