544 



YEINS. 



than the anterior ; and in old age it is more capacious than at an early period 

 of life. It receives veins from the pituitary body, and from the adjacent bone 

 and dura mater. 



The Inferior Petrosal Sinus is situated in the groove formed by the junction 

 of the inferior border of the petrous portion of the temporal with the basilar 

 process of the occipital. It commences in front at the termination of the 

 cavernous sinus, and opens behind, into the jugular foramen, forming with the 

 lateral sinus the commencement of the internal jugular vein. These sinuses are 

 semi-cylindrical in form. 



Fig. 306. The Sinuses at the Base of the Skull. 



The Transverse Sinus is placed transversely across the fore part of the basilar 

 process of the occipital bone serving to connect the two inferior petrosal and 

 cavernous sinuses. A second is occasionally found opposite the foramen magnum. 



The Superior Petrosal Sinus is situated along the upper border of the petrous 

 portion of the temporal bone, in the front part of the attached margin of the 

 tentorium. It is small and narrow, and connects together the cavernous and 

 lateral sinuses at each side. It receives a cerebral vein (inferior lateral cerebral) 

 from the under part of the middle lobe, and a cerebellar vein (anterior lateral 

 cerebellar) from the anterior border of the cerebellum. 



VEINS OF THE UPPER EXTEEMITY. 



The Yeins of the Upper Extremity are divided into two sets, superficial and 

 deep. 



The Superficial Veins are placed immediately beneath the integument be- 

 tween the two layers of superficial fascia ; they commence in the hand chiefly 

 on its dorsal aspect, where they form a more or less complete arch. 



The Deep Veins accompany the arteries, and constitute the venae comites of 

 those vessels. 



Both sets of vessels are provided with valves, which are more numerous in 

 the deep than in the superficial. 



