i8o APPLIED ANATOMY. 



of the arm. When it is paralyzed the arm cannot be raised beyond a right angle 

 and the scapula projects, particularly at its lower angle and posterior edge. This 

 condition is called ' ' winged scap^lla. ' ' 



The trapezius muscle (Fig. 203) has the shape of a triangle, its apex being out 

 on the acromion process and its base in the median line. It arises posteriorly from 

 the inner third of the superior curved line of the occiput, the occipital protuberance, 

 ligamentum nuchae, and the spines of the seventh cervical and all the thoracic vertebrae. 



It inserts into the outer third of the clavicle and the acromion and spinous proc- 

 esses of the scapula. It aids in rotating the scapula and elevating the shoulder; its 

 paralysis is followed by marked dropping of the shoulder. It is supplied by the 

 spinal accessory nerve, which is sometimes injured in operations for tumors involving 

 the posterior cervical triangle. 



The latissimus dorsi muscle arises from the spinous processes of the lower six 

 thoracic vertebrae, from the posterior layer of the lumbar fascia, the outer lip of the 

 posterior third of the iliac crest and by digitations from the lower three or four ribs. 

 Sometimes it is attached to the angle of the scapula. It unites with the tendon of the 

 teres major muscle to be inserted into the bottom of the bicipital groove and extends 

 somewhat higher than the tendon of the pectoralis major. A bursa, which may 

 become inflamed, sometimes lies between the muscle and the inferior angle of the 

 scapula. The latissimus dorsi and teres major muscles form the posterior axillary fold. 



The erector spinae (sacrospinalis) muscle fills up the hollows on each side of 

 the spinous processes. As the various muscular bundles are inserted into the vertebrae 

 by innumerable small tendinous slips, in exposing the vertebrae in performing lamin- 

 ectomy it is necessary to cut them with a knife or scissors. One should not attempt 

 to separate them by blunt dissection. These muscles become atrophied in cases in 

 which the spine becomes distorted. 



SURFACE ANATOMY OF THE THORAX. 



On looking at the chest one should note whether or not it appears normal. It 

 may show the rounded form of emphysema or the flat form of phthisis. One side 

 may be larger than the other, suggesting pleural effusion. The intercostal spaces 

 may be obliterated, indicating the same condition. This may be local instead of over 

 the whole chest. Note whether Harrison's groove, funnel and pigeon breast, or 

 beading of the ribs, already described, are present. Aneurism affecting the great 

 vessels may cause a bulging in the upper anterior portion, and cardiac disease may 

 produce marked changes in the apex beat. This may be displaced to the right side 

 by pleural effusion. 



The clavicle belongs to the shoulder-girdle and hence will be described with the 

 upper extremity. Both it and the sternum are subcutaneous and can readily be felt 

 beneath the skin. The point of junction of the first and second pieces of the sternum 

 is opposite the second costal cartilage. It forms a distinct prominence, which is 

 readily felt and is a most valuable landmark. It is called the anguhts stcrni or angle 

 of Liidzvig. There is usually a palpable depression at the junction of the second 

 piece of the sternum and xiphoid cartilage. 



The tip of the xiphoid or ensiform cartilage can be felt about 4 cm. below the 

 joint between it and the second piece of the sternum. The top of the sternum is oppo- 

 site the lower edge of the second thoracic vertebra. The angulus sterni is opposite 

 the fifth vertebra, the lower end of the second piece of the sternum is opposite the 

 tenth, and the tip of the ensiform cartilage is opposite the eleventh thoracic ver- 

 tebra. There is usually comparatively little fat over the sternum, so that in fat and 

 muscular people its level is below that of the chest on each side. Above its upper 

 end is the suprasternal notch or depression, below its lower end is the infrastcrnal 

 depression or epigastric fossa, sometimes called the scrobicuhis cordis. 



With the upper end of the sternum articulate the clavicles. The sternoclavicular 

 joint possesses an interarticular cartilage between the clavicle and the sternum. This 

 separates them sufficiently to allow the formation of a distinct depression, which can 

 readily be felt. From the sternum to the acromion process the clavicle is subcuta- 

 neous. Below the inner end of the clavicle the first rib can be often seen and felt. At 



