VENOUS SINUSES OF THE DURA MATER 



153 



PLEXUS MEDIALIS 



V CAPITIS PRIMA 



VESICULA AUDITIVA 



PLEXUS POST. 



Fig. 2 Drawing of the primary head vein and its tributaries in a human 

 embryo 13.8 mm. long (No. 940, Carnegie Collection). The point marked 'X' 

 is the junction of the intrinsic head-portion of the primary head vein with the 

 cardinal portion or internal jugular vein. Enlarged about 7 diameters. 



the 'anterior,^ 'middle^ and 'posterior cerebral veins.' The latter 

 two each empty into the main channel through a single trunk, 

 but the anterior cerebral vein maintains the character of the origi- 

 nal plexus and has multiple openings into the primary head vein. 

 Furthermore, the veins forming these three groups belong chiefly to 



