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 galli of the ethmoid bone ; behind, to the tcntorhnn cerebelli ; 

 above, to the inner surface of the caharium, 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 chords Willisii, 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 oerebri 



THIRD NERVE 



SECOND NER VE 



Tentorium 

 cerebeUi 



Lateral sinus 



Superior 

 petrusal sinus 



Falx oerebelli 



SEVENTH AND 

 EIGHTH 

 NERVES 



NINTH, TENTH, AND 

 ELEVENTH NER VES 



TWELFTH NER VE 



SECOND CERVICAL NERVE 



Ligamentum denticulatum 



FIFTH 

 NER VE 



FIRST 

 CERVICAL 



NER \ 'E Inferior petrosal sinus 



FIG. 82. THE CRANIUM OPENED TO SHOW THE FALX CEREKRI, THE TENTORIUM CEREBELLI, AI 

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



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

 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 petrosal 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. 



