122 



PRACTICAL ANATOMY. 



of the sphenoid bone. In its attached margin is the circular sinus. Under this 

 process of dura is the pituitary body. This body is connected to the tuber 

 cinerium on the floor of the third ventricle of the brain by the infundibulum, 

 which latter passes through an aperture in the diaphragma sellae. 



The falx cerebri (Fig. 82) is between the cerebral hemispheres. It is attached 

 in front to the crista galii of the ethmoid bone ; behind, to the teiitoriitin ccrcbclli ; 

 above, to the inner surface of the cahariitin, in the mid-line, and extends from 

 the tentorium to the crista galli. It contains in its attached margin the superior 

 longitudinal sinus; in its free margin its inferior longitudinal sinus. The 

 superior sinus contains the chorda' Wtflisii, mechanical devices for strengthening 

 and holding its walls together. Blood in this sinus flows from before backward ; 

 the sinus is fed by veins which open into it from behind forward. 



FOURTH NERVE 



Fall aerebri 



TIIIKD NKRVK 



SECOND NER VE 



Straight sinus 



Tentorium 

 oerebelli 



Lateral sinus 



Superior 

 petrusal xinta 



Fall oerebelli 

 SEVENTH AND 

 EIGHTH 

 NERVES 

 NINTH, TENTH, AND 

 ELEVENTH NERVES ^ 

 TWELFTH NER VE ' 



SECOND CERVICAL NERVE ' 



Ligamcntum donticulatum 



FIFTH 

 NER VE 



FIRST 

 CER VIC A L 



NER VE Inferior pctrosal sinut 



Middle 

 mrningeal 

 artery 

 Internal 

 carotid artery 



Verlrhral 

 artery 



FIG. 82. THE CRANIUM OPENED TO SHOW THE FALX CEREBRI, THE TENTORIUM CF.REUELU, AND 

 THE PLACES WHERE THE CRANIAL NERVES PIERCE THK DURA MATER. (Sappey.) 



The falx cerebelli is the smallest of the three large dural processes of the 

 dura. It is between the cerebellar hemispheres. Its attached margin corresponds 

 to the internal occipital crest of the occipital bone. It contains the occipital sinus. 



The tentorium cerebelli is midway, both in location and size, between the 

 two preceding processes. It is between the occipital lobes of the cerebrum and 

 the cerebellum. It protects the latter from the weight of the former. It is attached 

 to the horizontal part of the occipital crucial ridges posteriorly ; anteriorly and 

 laterally, to the superior border of the petrous portion of the temporal bone and 

 to the clinoid processes of the sphenoid bone. In the occipital attachment are 

 found the lateral sinuses ; in the temporal, the superior pctrosal sinuses. 



The dura mater has sinuses located as follows (Figs. 82 and 83) : 



1. Superior longitudinal, in the attached margin of the falx cerebri. 



2. Inferior longitudinal, in the free margin of the falx cerebri. 



3. Lateral, in the occipital attached margin of the tentorium cerebelli. 



