236 THE HEAD AND NECK 



be approached by the route described on p. 227 for the 

 reopening of the foramen of Magendie. The operation is 

 commonly performed in two stages, the first of which ceases 

 after the complete removal of the lower part of the squamous 

 portion of the occipital bone. In the second operation the occipi- 

 tal sinus is ligatured and divided along with the falx cerebelli 

 (p. 225). The cerebellum is displaced to the opposite side, 

 care being taken not to press it against the floor of the fourth 

 ventricle, and access is thus obtained to the cerebello-pontine 

 angle. 



