Till'. !!! AD AND NECK. 



127 



y. The Pia Mater. -As you have just observed, you can not remove the 

 arachnoid from the pia ; still, you can see perfectly the vessels of the pia mater 

 through the arachnoid. The presence of the subarachnoid tissue prevents 

 separation of these two structures. (Fig. 84.) The pia mater is composed, as 

 you can see on your dissection, of (i) arteries from the circle of Willis, taking 

 blood to the brain ; (2) veins attending these arteries, and finally opening into 

 the dural sinuses ; (3) connective tissue holding these arteries and veins, as the 

 warp of a carpet holds the woof. 



Remember, the individuality of the pia mater depends not on arteries alone, 

 not on veins alone, not on connective tissue alone ; but on all three woven 

 together, the connective tissue being the warp, the vessels the woof. 



Meninrjeal branch of 

 a iterior tthutniitul artery 



Mrninafal branch of pos- 

 terior ethmoidat artery 



Miilitle mtningeal 



OPHTBALHJC 



HI VISION OF 



FIFTH NER VE 



Tin It It NERVE 



Cavernous tiuits 



FOrllTII SERVE 

 AUDITORY AND 

 FACIAL NERVES 



; petrosal sintis 



Inferior petrosal sinus 



I'e.lro-sqritinwHS sinus 



.V/'/.YI/, .trri-.'-i- 



SORY NERVE 



^iifinoiil frorlion of 



lateral sinus 

 Posterior menintjeal 

 branch of vertebral 

 artery 

 Left marginal sinus 



Left lateral sitnts 

 Superior longitudinal sinus 



Circular sinus 

 Carotid artery 

 SIXTH NERVE 

 Basilar artery 

 Kasilar plexus of veint 

 A uditory artery 



Vertebral artery 

 I.-I.IIK.1II- I'll A R rXGKA L 



AlfD PXKUMOGASTRIO 

 Anterior tjtinat artery (ff. 



HYPOGLOStiAL 



NER VE 



SPINAL ACCES- 

 SORY NERVE 



Sight marginal sinus 

 Occipital sinus 

 Right lateral sinut 



FIG. 86. THE VKNOUS SINUSES. 

 (Krom a dissection by W. J. Walsham in St. Bartholomew's Hospital Museum.) 



Structures You See on the Base. Place the cadaver so the head will hang 

 over the end of the table. This position will permit the brain to gravitate to a 

 slight degree out of its bed. Gently shake the brain by rocking the head from 

 side to side. Notice now the following structures : 



1 . The frontal lobe of the cerebrum in the anterior fossa. 



2. The olfactory lobe, on the under surface of the frontal lobe. 



3. The optic chiasm and optic nerves. 



4. The internal carotid artery its cerebral stage. 



5. The third cranial nerve motor oculi. 



6. The tentorium cerebclli attached to the petrosa. 



Hints on Dissection of the Foregoing Structures. Gently retract the 

 frontal lobes and you will see the optic nerves covered by their prolongation of 



