VENOUS SINUSES OF THE DURA MATER 



165 



SIN. RECTUS 



SIN. SAGITTALIS SUP 



PLEXUS ANT 



SIN. TRANS. 



V. OPTHAL. 



Fig. 6 Profile reconstruction of the dural veins in a human embryo 50 mm. 

 long (No. 96, Carnegie Collection). The outlines of the veins of the falx cerebri 

 can be seen through the cerebral hemisphere. Enlarged about 4 diameters. 



does so. It constitutes what is known later as the 'tentorium 

 cerebeUi' and in it is included the greater part of the dural venous 

 system. A basal extension of the tentorium widens out in the 

 region of the semilunar ganglion and in its meshes is formed the 

 cavernous sinus. A thinner area of the same tissue extends 

 caudalward from the cavernous sinus, medial to the otic capsule, 

 to join the jugular region. The slender plexus of veins extend- 

 ing through this constitutes the inferior petrosal sinus. Along 

 all the sinuses we find this same areolar meshwork. It is not 



