THE HEAD AND NECK. 



127 



9. 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. 



Meningeal branch, of 

 anterior ethmoidal artery 



Jfeningfal branch of pos- 

 terior ethmoidal artery 



Middle meningeal 



artery 



OPHTHALMIC 



DIVISION OF 



FIFTH NERVE 



THIRD NER YE 



Cavernous sinus 

 FOl'RTH NERVE 

 AUDITORY AND 

 FACIAL NERVES 



Superior petrosal sinus 

 Inferior petrosal sin-as 

 Petro-sijiiamous sinus 

 SPINAL ACCES- 

 SOR Y NER VE 

 Sigmoid portion of 



lateral sinus 

 Posterior menimjeal 

 bran ch of vertebral 

 artery 

 Left marginal sinus 



Left lateral sinus 

 Superior longitudinal sinus 



Circular sinus 

 Carotid artery 

 SIXTH NERVE 

 Basilar artery 

 Basilar plexus of veins 



Auditory artery 

 Vertebral artery 

 GLOSSO-PHARYNGEAL 



AND PNEUMOGASTRIO 

 Anterior spinal artery [N. 

 HYPOGLOSSAL 



NER VE 

 SPIN A L A CCES- 



SOR Y NER VE 



Right marginal sinus 



cipilal sinus 

 Right lateral sinus 



FIG. 86. THE VENOUS SINUSKS. 

 (From 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 cerebelli 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 



