DISSECTION OF THE UPPER EXTREMITY 71 



Divide the M. deltoideus close to its origin and reflect it 

 downward, avoiding injury to the ramus acromialis of the A. 

 thoraco-acromialis. Examine carefully the subdeltoid bursa 

 (bursa subdeltoidea) and the subacromial bursa (bursa sub- 

 acromialis). 



Beneath the deltoid dissect out carefully 



(a) Posterior circumflex artery of humerus (A. circumftexa humeri pos- 



terior). 



(b) Anterior circumflex artery of humerus (A. circumftexa humeri an- 



terior). 



(c) Veins corresponding to these arteries. 



(d) Axillary nerve (N. axillaris) (0. T. circumflex). 



(da) Muscular rami (rami musculares). 



(daa) N. teres minor. 



(dab) Nn. deltoidei. 



(db) Lateral cutaneous nerve of the upper arm (N. cutaneus 



brachii lateralis). 



Teres Major Muscle (M. teres major) ("Larger Round Muscle"). 

 Study carefully its form, position, origin, insertion, action, 

 and innervation. Note especially the torsion the muscle un- 

 dergoes. Review the relation of this muscle to the quadrilateral 

 and triangular spaces. Between the tendon of insertion and 

 the bone find the bursa of this muscle (bursa M. teretis ma- 

 joris). Between the tendon of the M. teres major and that of 

 the M. latissimus dorsi find the bursa of the latter muscle 

 (bursa M. latissimi dorsi). Do you find any trace of a M. 

 dorsi-epitrochlearis ? Examine carefully at this stage the 

 exact mode of termination of the tendons of the Mm. pectoralis 

 major and latissimus dorsi. 



Ligaments of Shoulder-blade and Acromioclavicular Articulation. 



Ligaments of the shoulder-blade. Study 



(a) Coraco-acromial ligament (ligamentum coraco-acromiale) . 



(b) Superior transverse ligament of scapula (Lig. transversum scapulae 



inferius). 



(The latter will be seen at a later stage of the dissection.) 

 Acromioclavicular articulation (articulatio acromioclavicularis) . Study 



(a) Joint-capsule (capsula articulari$) . 



(b) Acromioclavicular ligament (ligamentum acromioclaviculare) . 



(c) Intercalated disk of fibrocartilage (discus articularis) . Is one 



present ? 



(d) Coracoclavicular ligament (ligamentum coracoclaviculare) . 



(da) Anterior, lateral, quadrangular part, or trapezoid ligament 

 (Lig. trapezoideum) . 



