2S 



DISSECTION OF THE UPPER LIMB. 



origin ; 



insertion ; 



three parts 

 the muscle ; 



relations 



of the chest to the base of the scapula, and clothes the inner wall 

 of the axilla. It arises from the upper eight or nine ribs by as 

 many slips or digitations, and passes backwards, diminishing in 

 breadth, to be inserted into the whole length of the base of the 

 scapula on the ventral aspect. From a difference in the arrangement 

 of the slips, the muscle is divided into three parts : 



The upper part is formed by the first digitation, which is thicker 

 than the others, and springs from the first and second ribs, as well 

 as from a tendinous arch between them : it is inserted into an 

 impression in front of the upper angle of the scapula. The middle 

 part is thin, and comprises two digitations, which spread out from 

 the second and third ribs to the vertebral border of the scapula. 

 The lower part is the strongest, and consists of the remaining five 

 or six slips, which converge from their ribs (fourth to eighth or 

 ninth) to a special surface on the ventral aspect of the lower angle 

 of the scapula. 



The serratus is in great part concealed by the pectoral muscles, 

 the axillary vessels and nerves, and the scapula, with the subscapu- 

 laris and latissimus dorsi muscles. Its deep surface rests against 

 the ribs and the intercostal muscles. The lower slips interdigitate 

 with like processes of the external oblique muscle. 



Action. The whole muscle acting, the scapula is carried forwards. 

 But the lower part can move forwards the lower angle alone, so as 

 to rotate the bone, and turn the glenoid cavity upwards as in 

 raising the arm above the level of the shoulder. The lowest slips 

 may evert the ribs in forced inspiration. 



Removal of the limb. The limb is now to be drawn away 

 from the side of the body and removed by cutting through the 

 serratus magnus muscle about an inch from its insertion into the 

 vertebral border of the scapula, by dividing the omohyoid muscle 

 and the suprascapular vessels and nerves near the upper border of 

 the bone and the latissimus dorsi near the lower angle. The 

 ligatures embracing the axillary vessels and the nerves of the 

 brachial plexus should be fixed to the outer fragment of the clavicle 

 or to the subjacent soft parts, so as to retain them approximately in 

 their position. 



Position. 



Dissection 

 of muscles. 



SECTION II. 



SCAPULAE MUSCLES, VESSELS, NERVES, AND LIGAMENTS. 



Position. After the limb has been separated from the trunk it 

 is to be placed with the subscapularis uppermost. 



Dissection. The different muscles that have been traced to the 

 scapula in the dissection of the front of the chest and of the back 

 are now to be followed to their insertion into the bone. A small 

 part of each, about an inch in length, should be left for the pur- 

 pose of showing the attachment. 



Fig. 10 shows the attachments of the muscles to the ventral 

 surface of the bone, and fig. 12 (p. 32) to the dorsal surface. 



