12 DISSECTION OF THE UPPER LIMB. 



clavicle, corresponds with the interval between the clavicular and! 

 the sternal origins of the great pectoral muscle. 

 Ann : its Along the front of the arm is the prominence of the biceps! 



andTwves 111U8C ^ e 5 anc * on eacn s ^ e ^ tnat em i n e nce is a groove, which sub-l 

 sides inferiorly in a depression in front of the elbow-joint. The 

 groove on the inner side of the biceps is the deeper, and indicates ; 

 the position of the brachial vessels. 



Promi- If the elbow-joint be slightly flexed, the prominences of the 



around the ou t er and inner condyles of the humerus will be rendered evident, 



elbow-joint, especially the inner. Below the outer condyle, and separated 

 from it by a slight interval, the head of the radius is placed, and 

 may be recognised by rotating that bone, the fingers at the same 

 time being placed over the head. At the back of the elbow is the 

 prominence of the olecranon, and to the outer side of this, when the 

 forearm is fully bent, a projection is formed by the capitellum. 



Dissection. The first step in the dissection is to raise the skm 

 from the side of the chest and the armpit, over the great pectoral 

 muscle and the hollow of the axilla, by means of the following 



incisions, incisions : One is to be made along the middle of the sternum 

 (fig. 1, B. 2). A second is carried along the whole length of dark-It- 

 and continued downwards over the outer side of the shoulder for 

 about three inches (fig. 1, B. 5). From the lower end of the sternum 

 a third cut is to be directed outwards over the side of the chest, 

 as far back as to a level with the posterior fold of the armpit 

 (fig. 1, B. 7), and a fourth is taken upwards and outwards from the 

 lower end of the sternum along the anterior folds of the axilla on to 

 the arm opposite the lower end of the shoulder cut (fig. 1, B. 6). 



Reflect skin. The flaps of skin thus marked out are to be reflected outwards 

 beyond the axilla ; but they should be left attached to the body, in 

 order that they may be used for the preservation of the part. 



Superficial The subcutaneous fatty layer of the thorax resembles the same 



fascia. structure in other parts of the body ; but in this region it does not 

 usually contain much fat. 



Deep fascia : Beneath the subcutaneous layer is the stronger deep fascia, which 

 closely invests the muscles, and is continuous with the fascia of the 

 arm. It is thin on the front of the chest, but becomes thick where 



thickest it is stretched across the axilla. An incision through it, over the 



over axilla. arm pi^ \yill render evident its increased strength in this situation, 

 and the casing that it gives to the muscles bounding the axilla ; and 

 if the forefinger be introduced through the opening, some idea will 

 be gained of its capability of confining an abscess in that hollow. 



Cutaneous Dissection. The cutaneous nerves of the side of the chest are 

 first to be sought. At the spots where they are to be found 

 they are placed beneath the fat, which must be cut through to 

 expose them ; and those over the clavicle lie also beneath the super- 

 ficial platysma muscle. Small vessels for the most part accompany 

 the nerves, and indicate their position. 



from cervi- Some of the nerves (from the cervical plexus) cross the clavicle 

 at the middle, and the inner end. Others (anterior cutaneous of the 

 thorax) appear at the side of the sternum, one through each inter- 



