DISSECTION OF THE HEAD AND NECK. 163 



Ligaments of the Processes and Neural Arches :— 



The Liff amentum JVuchce. —This has already been dissected. 



The Interspinous Liffaments.— These are composed of yellow elastic 

 tissue. Each consists of two narrow parallel bands stretching between 

 adjacent superior spinous processes. 



Capsular ligaments of the articular processes. 



Ligamentum subflava. — For these two series of ligaments, see page 138, 

 where the corresponding ligaments of the back and loins are described. 

 In the neck these ligaments differ from those of the other regions in 

 being composed of yellow elastic tissue. 



Ligaments of the Bodies : — 



The Superior Common Ligament lies on the floor of the spinal canal 

 and terminates in front at the axis. See page 139. 



The Intervertebral Substance. See page 139. 



Movements of the cervical part of the spinal column. These are 

 flexion, extension, lateral inclination, rotatimi, and circumduction, the last 

 being a combination of the first three. In flexion the vertebrte are 

 carried downwards in a vertical plane, and extension is the opposite 

 movement. Rotation is the twisting or turning of a vertebra round 

 a longitudinal axis passing through its body. In consequence of the 

 thickness of the intervertebral substance, and the feeble development of 

 the transverse and spinous processes, all these movements have 

 here a greater range than in the back or loins ; and within the 

 cervical region the greatest range of movement is permitted in the 

 posterior joints. 



THE EXTERNAL EAR (fIG. 20). 



The organ of hearing consists of three divisions — the external, the 

 middle, and the internal ear. Only the first of these will now be 

 examined. The middle and the internal ear, which are cavities within 

 the petrous temporal bone, are described at page 275. The external ear 

 comprises the external auditory process of the petrous temporal bone ; 

 three cartilages — concha], scutiform, and annular ; muscles which move 

 these cartilages ; vessels ; and nerves. 



Directions. — An incision through the skin is to be begun a few inches 

 behind the summit of the occipital bone, and carried down the middle 

 line as far as the supraorbital process. It is here to be carried outwards 

 along the supraorbital process, and then backwards along the zygomatic 

 arch. On reaching the articulation of the jaw the incision should be 

 carried along the edge of the vertical ramus, and inwards to the middle 

 line. All the skin mapped out by this incision is to be removed, the 

 conchal cartilage being also denuded of its outer covering. This will 

 expose not only the parts of the external ear, but also the parotideal 

 region and the poll, and the dissection of these parts is to be made as 



