206 



HEAD AND NECK 



the lateral lacuna. The inferior angle of the channel is 

 crossed by a number of minute bands, named chorda Willisii', 

 and arachnoideal granulations bulge into it. The mouths of 

 the superior cerebral veins open into the sinus, or into the 

 lateral lacunae, pouring their blood into the sinus in a direc- 

 tion contrary to that in which the blood flows within the 



Falx cerebri 



Inferior sagittal sinus 

 Superior sagittal 

 sinus 



Cavernous sinus 



Vena cerebri magna 



Tentorium 



Auditory 

 tube 



Transverse sinus 



Inferior petrosal sinus Superior petrosal sinus 



FIG. 86. Sagittal section through the Skull a little to the left of the 

 median plane to show the processes of Dura Mater. 



V. Trigeminal nerve. 

 VII. Facial nerve. 

 VIII. Acustic nerve. 



IX. Glossopharyngeal nerve. 



X. Vagus nerve. 

 XI. Accessory nerve. 

 XII. Hypoglossal nerve. 



channel that is, the terminal portions of the veins are directed 

 anteriorly, whilst the blood in the sinus flows posteriorly. 



The Relation of the Arachnoideal Granulations to the Superior 

 Sagittal Sinus and the Lateral Lacunae. When the granulations push 

 themselves into the sinus or the lateral lacunae they push before them a 

 thin continuous covering of the floor of the space, and when they project 

 still further and encroach upon the bones of the skull they are covered also 

 by a thin expansion of the roof of the space. 



Falx Cerebri (Figs. 86, 87). This is a sickle-shaped redupli- 

 cation of the inner layer of the dura mater, which descends 

 in the median plane, between the two cerebral hemispheres. 



