THE ANTERIOR LIMB 261 



posterior part of the origin, is attached more obliquely, just in front of 

 the intertubercular groove and along the medial edge of the spine of 

 the humerus, ending at the tip of that ridge. 



(d) The pectoralis tertius (p. minor). Origin consisting of two 

 portions. First portion: The sternum from its anterior 

 end to the attachment of the fourth rib. Second portion: 

 On the manubrium sterni from its anterior end to a point a 

 little behind the attachment of the first costal cartilage 

 and on this cartilage, lying dorsal to the first portion. 

 Insertion: The superficial fibres of the first portion are 

 attached to the clavicle. The remaining fibres, combined 

 with those of the second portion and those of the pecto- 

 scapularis, pass to the dorsal side of the clavicle and over 

 the shoulder to be inserted on the ventral fourth of the 

 scapular spine, the supraspinous fascia (p. 264), and both 

 surfaces of the medial angle of the scapula. The muscle 

 forms a broad fleshy mass covering the anterodorsal portion 

 of the shoulder. 



(e) The pectoralis quartus. Origin: The sternum, from the 

 attachment of the fourth to seventh costal cartilages. In- 

 sertion: Anterior surface of the head of the humerus, 

 passing thence to its medial side. The muscle overlaps the 

 posterior edge of the first portion of (d) and the thoracoa- 

 cromial artery passes between them. 



(/) The pectoscapularis. Origin: The manubrium sterni at 

 the point of attachment of the first costal cartilage. In- 

 sertion as indicated above. A slender muscle dorsal to the 

 first portion of the p. tertius, which should be divided, and 

 overlapping ventrally the posterior edge of the second 

 portion. 



Blood-Vessels and Nerves of the Axillary Fossa 



After division of the pectorals and the clavicle, the blood- 

 vessels and nerves of the axillary fossa will be fully exposed. 



During the examination of these, the axillary lymph glands may be noted. 

 In speciall}' injected preparations, these are found to receive superficial and deep 

 lymphatic vessels from the anterior limb and to drain into the subclavian trunk, 

 which accompanies the corresponding vein and opens into the superior vena cava. 



