The Anterior Limb. 205 



VUI. THE ANTERIOR LIMB. 



For this dissection the skin must first be reflected from the 

 lateral surface of the limb and the side of the neck to the dorsal 

 median line. It is advisable to divide the skin at the elbow, 

 leaving the forearm and hand covered, so that the tendons of the 

 muscles do not become dried out before they can be examined. 



Covering the side and ventral surface of the neck is a broad thin 

 sheet of muscle, the platysma, replacing the cutaneus maximus 

 of the trunk. It forms a continuous layer over the dorsal surface 

 of the neck, at which place it is also continuous with the cutaneus 

 maximus. Passing forward from the manubrium sterni is a narrow 

 band of fibres, inseparable from the platysma but lying beneath it, 

 the depressor conchae (parotideoauricularis) posterior, which 

 is inserted into the external base of the ear. The entire sheet of 

 muscle is so closely attached to the skin that it is sometimes re- 

 moved with the latter. If in place it should be raised from the 

 surface, separated posteriorly from its attachment, and turned 

 forward on the head. 



The dissection is mainly muscular, but the arteries and. nerves 

 should, be kept intact for later examination. 



Identify the manubrium sterni. The muscle directed forward 

 from it toward the angle of the mandible is the sternomastoideus, 

 one of the muscles of the head. The external jugular vein lies on 

 its lateral side. Identify the clavicle rudiment and the cleido- 

 humeral ligament; then proceed to uncover the muscles directed 

 forward, from this region to the head. 



For the general muscle relations of the limbs, see p. 64. 

 *I. Muscles arising from the axial skeleton and inserted, on the 

 scapula and clavicle. 



(a) The cleidomastoideus. Origin: Mastoid portion of the 



skull. Insertion: Middle portion of the clavicle. 



The muscle King on its medial side and arising from the manu- 

 brium sterni is the sternomastoideus, one of the muscles of the head. 



*The structures of Group 2 may be dissected first if preferred, the serratus 

 anterior muscle being exposed from the lateral surface and divided together with 

 the latissimus dorsi. 



