SITUS VISCERUM. 463 



b. Art. fossce Sylvii [middle cerebral], commences below the 

 lamina cribrosa, then in fossa Sylvii. 



c. Art. choroidea, external tocrus cerebri, below tractus opticus, 

 enters the cornu descend, of the lateral ventricle. 



2. Circidus arteriosus Willisii, above and close to the sella tur- 

 cica, surrounds the chiasma, tuber cinereum and corp. mam- 

 millaria. 



3. Art. vertebralis, enters into the cranial cavity at the posterior 

 lateral part offoram. magn., lies at first on the side of, then ob- 

 liquely before the medulla oblongata. The two vessels unite and 

 pass as basilaris upon the clivus. 



a. Art. basilaris gives off: art. auditories internee, cerebelli in- 

 feriores and superiores, and divides at the proc. clinoid. 

 post, into the two artt. profunda cerebri [posterior cerebral], 

 which pass around the crura cerebri to the posterior cerebral 

 lobes. 



714. Thorax [compare 695.] 



After removing the sternum we arrive at the pleura with the 

 lungs laterally, in the centre the cavum mediastini antici, the 

 pericardium with the heart, and the cavum mediastin. postic. with 

 trachea, oesophagus, vascular and nervous trunks. 



715. I. Pleurae. Each pleural sac is united to the lateral 

 thoracic parietes as pleura costalis. The right lies obliquely from 

 above to below, and from right to left, so that above it reaches as 

 far as the right border of manubrium sterni, below to the centre 

 of corp. sterni. The left attaches itself to the left border of the 

 manubrium, below to the external extremity of the sixth and 

 seventh rib cartilage. 



From these points the pleura costalis turns backwards on either 

 side to the lateral regions of the pericardium and the roots of the 

 lungs as mediastinum anticum. 



Each pleura costalis goes backwards to the front of the heads 

 of the ribs and to the sides of the vertebral bodies, and hence turns 

 forwards to the lateral surfaces of the pericardium and to the roots 

 of the lungs as mediastin. posticum. 



Below, the pleura is united with the convex surfaces of the dia- 

 phragm, pleura phrenica ; posteriorly and at the sides it extends 

 to the last ribs. 



Ligamentum pulmonis, extends from the pleura phrenica to 

 the posterior border of the inferior lobe of the lungs, and here 

 passes over into the 



Pleura pulmonalis, which invests the entire surface of the lungs, 



