DUE A MATER AND SINUSES. 29 



portion of the temporal bone these sinuses turn downward, 

 and pass through the posterior foramen lacerum ; just 

 before entering the foramen the inferior petrosal sinus joins 

 the lateral sinus, and the two united become the internal 

 jugular vein. 



The inferior petrosal sinus is the continuation backward 

 of the cavernous sinus ; it passes along the lower border of 

 the petrous portion of the temporal bone, and terminates 

 as above described. The superior petrosal sinus is of small 

 size, and lies along the upper border of the petrous bone 

 in the attached portion of the tentorium ; it establishes 

 another communication between the cavernous and lateral 

 sinuses, by entering the latter near the base of the petrous 

 bone. 



Projecting below the tentorium is the falx cerebelli, 

 which separates the two hemispheres of the cerebellum as 

 the falx cerebri does those of the cerebrum ; it ends at the 

 foramen magnum, and is attached along the middle line of 

 the occipital bone. In the attached border of this falx may 

 be found two small sinuses, called the occipital sinuses, 

 which terminate in the torcular Herophili. 



The cavernous sinuses are situated on each side of the 

 sell a turcica, and are so called from the existence, in their 

 interior, of trabeculae, like those of cavernous structures in 

 other parts of the body. In the internal wall of the sinus 

 is the internal carotid artery, covered by minute nervous 

 ii laments of the carotid plexus of the sympathetic nerve, 

 and crossed by the sixth or abducens nerve ; in the external 

 wall of the sinus are the third (motor oculi), fourth (tro- 

 chlearis), and ophthalmic branch of the fifth or trifacial 

 nerve. 



The cavernous sinuses of the two sides are connected by 

 the circular sinuses, which surround the pituitary gland ; 

 the transverse, or hasilar sinus, which lies upon the basilar 

 portion of the occipital bone, sometimes unites the cavern- 

 ous and sometimes the petrosal sinuses ; anteriorly, they 

 receive the ophthalmic veins, which, after collecting the 

 blood from the eye and structures within the orbit, enter 

 the sinus through the sphenoidal fissure. 



The PITUITARY BODY should be sought for in the sella 

 turcica and removed for examination. It is a reddish- 

 gray, solid bod}r, closely fixed in its location by the dura 

 mater ; it is composed of two lobes, the anterior of which 

 is the largest ; and is connected with the infundibulum of 



