312 TEE MUSCLES. 



of these two muscles. Thick inferiorly, this portion diminishes considerably 

 towards its superior extremity. 



Structure and Attachments. — The first portion is generally paler than the 

 second, and is composed of longitudinal fleshy fibres deeply intersected by tendi- 

 nous strips. It takes its origin, by its superior extremity, from the dorsal angle 

 of the scapula. The anterior portion is deeper-coloured and more tendinous 

 than the other. Its superior extremity, included within two fibrous folds 

 resulting from the duplicature of the scapular aponeurosis, is fixed, through the 

 medium of these, to the tuberosity of the scapular spine. 



These two muscular bodies unite inferiorly, and terminate together on the 

 deltoid imprint or crest by tendinous and muscular fasciculi. 



Relations. — Outwardly, to the scapular aponeurosis, with which it may be said 

 to form one body ; inwardly, to the infra-spinatus, the short abductor of the 

 arm, and the large and short extensors of the forearm. 



Action. — It gives a very marked abduction movement to the humerus, and 

 also makes it pivot outwards. It acts, besides, as a flexor of that bone, when its 

 action is combined with that of the adductor of the arm. It should also be con- 

 sidered as a powerful tensor of the scapular aponeurosis. 



3. Short Abductor of the Arm (Postea Spinatus Minor), or Teres 

 Minor (Fig. 128, 2, 3). 



Synonyms. — Scapulo-humeralis minor — Girard. (Scapulo'trochiterim, medimi and parvum 

 ^Leyh.) 



Volume — Situation — Direction. — A small elongated muscle, situated below the 

 preceding and the subspinatus, along the posterior border of the scapula, the 

 direction of which it follows. 



Form — Structure. — In its inferior half it is prismatic, muscular, divided by 

 fibrous intersections, and easily separated into several irregular fasciculi. In its 

 superior half it is flattened, entirely tendinous, and split into several digitations, 

 the longest of which are behind. 



Attachments. — It originates : 1. Through the medium of its tendinous digita- 

 tions, from the posterior border of the scapula and the linear imprints in the 

 infra-spinous fossa. 2. From the small tubercle situated on the external side 

 of the margin of the glenoid cavity, by a short tendon. It tenninates on the 

 humerus, between the crest of the external tubercle and the deltoid imprint. 



Relations. — Outwardly, with the infra-spinatus and the long abductor ; 

 inwardly, with the large extensor of the forearm, the short extensor, and the 

 capsule of the scapulo-humeral articulation. 



Action. — Like the preceding, this muscle is an abductor and outward rotator 

 of the humerus. 



4. Supra-spinatus (AfJTEA-SPiNATUS) (Figs. 179, 2 ; 181, 5). 



iSi/Tioni/mg.—Supra-acromio-trocliiterius— Girard. (^Antea spinatus — Percivall. Anterior 

 spinatus — Leyh.) 



Form — Situation. — This muscle is thick and prismatic, stronger below than 

 above, representing a very elongated pyi-amid, and completely filling, and even 

 projecting beyond, the supra-scapular fossa. 



Structure — Attachments. — It is almost entirely formed of fleshy fibres, which 

 are attached, by their superior extremities, to the cartilage of prolongation of the 



