DISSECTION OF THE UPPER EXTREMITY 



53 



(b) From the processus xiphoideus lateralward to the back. 



(c) From the upper end of the first incision lateralward along the clavicle 



to the tip of the acromion. 



(d) From the processus xiphoideus obliquely upward and lateralward 



along the plica axillaris anterior as far as the brachium. 



FlG. 7. 



With a sharp knife dissect up the two triangular flaps marked 

 out by the incisions mentioned. Keep the knife close to the white 

 corium so that none of the fat 

 of the superficial fascia is re- 

 moved with the skin. 



Compare the amount of fat 

 in the superficial fascia in your 

 subject with that in neighboring 

 subjects. Find the fibres of the 

 platysma streaming down into it 

 over the clavicle. Note that the 

 mammary gland is situated in 

 the superficial fascia. Cut boldly 

 through the superficial fascia 

 down to the deep fascia in the 

 middle line in front, and then 

 with the blunt probe dissect up 

 the superficial fascia, passing 

 gradually lateralward. Find the 

 cutaneous blood-vessels and 

 nerves passing into the super- 

 ficial fascia from the depth. 

 When the trunks of these are 

 found, follow each carefully out 

 as far as possible into the super- 

 ficial fascia, cleaning it care- 

 fully. Avoid injury to the 

 superficial nerves which pass 

 down over the clavicle. Keep 

 your atlases open before you as 

 a guide to the location of the various structures. As soon as 

 a nerve or blood-vessel is found, identify it, getting the name 

 from the atlas. Find a description of it in your systematic 

 text-book of anatomy (using the index of the latter) and com- 

 pare the actual findings in your subject with the text-book de- 

 scription. Note especially any differences between your object- 

 ive findings and the printed descriptions. 



Skin incisions on the anterior surfaces of the body 



