REMOVAL OF THE BRAIN 



221 



with the accompanying venous channels, occupy the arbor- 

 escent grooves on the inner surface of the cranial vault. 



The vein which accompanies the middle meningeal artery 

 passes through the foramen spinosum and ends in the plexus 

 around the external pterygoid muscle. 



Each anterior meningeal artery proceeds from the anterior 

 ethmoidal artery as it accompanies the anterior ethmoidal 

 nerve across the cribriform plate of the ethmoid bone. 

 It supplies a limited area of dura mater and bone in the 

 anterior fossa of the cranium. 



The accessory meningeal arteries (O.T. small meningeal] are 

 somewhat inconstant; they arise either directly from the 



FIG. 91. i, Hypophysis ; 2, in median section ; 

 3, in horizontal section. (Schwalbe. ) 



a. Anterior lobe. 



b. Posterior lobe. 

 cm. Corpus mamillare. 



i. Tuber cinereum. 



ch. Optic chiasma in section. 



ro. Optic recess of the third ventricle. 

 o. Optic nerve. 

 a'. Infundibulum with projection from 



anterior lobe upwards anterior 



to it. 



internal maxillary or from the middle meningeal. Each 

 enters the cranium through the corresponding foramen ovale, 

 but it should not be looked for at the present stage, as it 

 is best examined along with the semilunar (O.T. Gasserian) 

 ganglion and the three divisions of the trigeminal nerve. 



The meningeal branches from the ascending pharyngeal arteries 

 are the terminal twigs of those vessels. They enter the 

 cranium through the lacerate and jugular foramina, and 

 through the hypoglossal canal (O.T. anterior condyloid 

 foramen). The branch which passes through the jugular 

 foramen is the largest. 



The meningeal branches of the occipital and vertebral arteries 

 are small, and are distributed in the posterior cranial fossa. 

 The former enter through the jugular, mastoid, and parietal 

 foramina, the latter through the foramen magnum. 



