THE ACROMIAL REGION 463 



nost distinct in front of the elbow, and contains very large superficial veins and 

 lerves; in the hand it is hardly demonstrable, the integument being closely ad- 

 terent to the deep fascia by dense fibrous bands. Small subcutaneous bursse 

 ,re found in this fascia over the acromion, the olecranon, and the knuckles. 



The deep fascia of the upper extremity comprises the aponeurosis of the shoulder. 

 ,rm, and forearm, the anterior and posterior annular ligaments of the carpus, 

 nd the palmar fascia. These will be considered in the description of the muscles 

 f the several regions. 



3. The Acromial Region. 

 Deltoid. 



The deep fascia covering the Deltoid invests this muscle and sends down numer- 

 >us prolongations between its fasciculi. In front, it is continuous with the fascia 

 overing the great Pectoral muscle; behind, with that covering the Infraspinatus; 

 'hove, it is attached to the clavicle, the acromion, and spine of the scapula; below, 

 t is continuous with the deep fascia of the arm. 



The Deltoid (m. deltoideus) (Fig. 347) is a large, thick, triangular muscle, which 

 jives the rounded outline to the shoulder, and has received its name from its resem- 

 dance to the Greek letter J (delta) inverted. It covers the shoulder-joint in front, 

 >ehind, and on its outer side. It arises from the outer third of^rhp qpt 

 nd uprjgr_surface of the clavicleY from the outer margin and upper s 

 lie acromion process, and from the lower lip ofthejKjsterior border nf t 

 if the scapula, as far back as the triangular surfaceat its mesal end. From this 

 xtensive origin the* fibres converge toward their insertion, the middle passing 

 ertically, the anterior obliquely backward, the posterior obliquely forward, 

 hey unite to form a thick tendon, which is iti^erted mioa^rough triangular promi- 

 lence on themiddle of the outer side nfjjie_^ha.fiU>f the, hnmerny^ At its insp'rtinn 

 he muscIfTgives 7)ff an~expansion tcTthe deep fascia of the arm. This muscle 

 s remarkably coarse in texture, and the arrangement of its muscle fibres is some- 

 rhat peculiar; the central portion of the muscle that is to say, the part arising 

 rom the acromion process consists of fibres having an oblique direction, 

 rhich arise in a bipenniform manner from the sides of tendinous intersections, 

 ;enerallv four in number, which are attached above to the acromion process and 

 ass downward parallel to one another in the substance of the muscle. The 

 iblique muscle fibres thus formed are inserted into similar tendinous intersec- 

 ions, generally three in number, which pass upward from the insertion of the 

 nuscle into the humerus and alternate with the descending septa. The portions 

 >f the muscle which arise from the clavicle and spine of the scapula are not 

 rranged in this manner, but pass from their origin above, to be inserted into 

 he margins of the inferior tendon. 



Relations. By its superficial surface, the Deltoid is in relation with the integument, the 

 uperficial and deep fasciae, Platysma, and supra-acromial nerves. Its deep surface is separated 

 rom the capsule of the shoulder-joint by a large sacculated synovial bursa, the subdeltoid 

 lursa (bursa xubdeltmdea). It often communicates with the subacromial bursa (bursa sub- 

 cromialis), which is between the acromial process and the coraco-acromial ligament above and 

 he capsule of the shoulder-joint and the Supraspinatus muscle below. The deep surface of 

 he Deltoid covers the coracoid process, coraco-acromial ligament, Pectoralis minor, Coraco- 

 irachialis, both heads of the Biceps, the tendon of the Pectoralis major, the insertions of the 

 mpraspinatus, Infraspinatus, and Teres minor, the scapular and external heads of the Triceps, 

 he circumflex vessels and nerve, and the humerus. Its anterior border is separated at is upper 

 >art from the Pectoralis major by a cellular interspace, which lodges the cephalic vein and 

 mineral branch of the acromiothoracic artery; lower down the two muscles are in close con- 

 act. Its posterior border rests on the Infraspinatus and Triceps muscles. 



Nerves. The Deltoid is supplied by the fifth and sixth cervical through the circumflex nerve. 



