146 THE PRINCIPLES OF MYODYNAMICS. 



left rectus capitis lateralis, the left superior ob- 

 lique, the left trapezius, the left splenius capitis, 

 the left trachelo-mastoid, and the left sterno- 

 cleido-mastoid. 



(b.) (i.) The flexion and extension of the skull 

 take place mostly at the cranio-atloid joint, 

 (ii.) The rotation of the skull takes place mostly 

 at the atlo-axoid joint, (iii.) The adduction of 

 the skull takes place mostly in the cervical spine 

 below the axis and in the cranio-atloid joint. 



(c.) The term adduction designates the fact 

 that the head^ as it is bent to the right or to the 

 left, approaches the body on the side to which 

 the movement is made. The term ab-duction 

 would designate the fact that the head, as it is 

 bent to the right or to the left, moves as a 

 whole from the long axis of the body. Either 

 term would be appropriate, though the former 

 has been used. 



137. The skull is a lever of the first order, in 

 which : ( i .) The pozver is derived from one or 

 more muscles — assisted at times by the weight 

 of some part of the head; and in which : (2.) 



