VENOUS SINUSES OF THE DURA MATER 



159 



PLEXUS ANT. 



SIN. TRANSVtR5US 



PLEXUS POST. 



N TRIGEMINUS 



ilN CA\'ERNOSUS 



Fig. 4 Profile reconstruction of the veins of the dura mater in a human 

 embryo 21 mm. long (No. 460, Carnegie Collection). The vein marked 'x' is the 

 remnant of the otic portion of the primary head vein which originally connected 

 the cavernous region with the internal jugular vein. The outlines of the central 

 nervous system in this model were taken from a model made by Professor Lewis. 

 Enlarged 10 diameters. 



gives a different origin for the superior petrosal sinus. According 

 to him (p. 599), it takes its origin from a small cerebral vein de- 

 rived from the basal surface of the hind-brain which empties into 

 the V. prootica. In the further development, the opening of the 

 vein migrates by anastomoses along the v. prootica toward the 

 sinus transversus and either empties into that sinus or into the 

 V. prootica near it. According to him, the superior petrosal sinus 



