44 A MANUAL OF ANA TOMY. 



The Circular Sinus. Diag. 2. 



Connects the two cavernous sinuses in front and behind 

 the pituitary body, which it encloses in a venous circuit. 



The Transverse Sinus. Diag. 2. 



This is really a venous plexus upon the basilar process 

 of the occipital bone, joining the two inferior petrosal si- 

 nuses and communicating with the spinal veins below. 



DISSECTION. 



Trace out the middle meningeal artery, noting how deeply its trunk and the 

 beginning of the anterior and posterior branches groove the bone, sometimes 

 being bridged over with bone at the anterior inferior angle of the parietal 

 bone. 



Clean the stumps of the second to twelfth cranial nerves from before back- 

 ward and learn their foramina of exit. 



Trace the nerves and internal carotid artery, which pass through the caver- 

 nous sinus, and follow the carotid artery until it disappears through the middle 

 lacerated foramen. 



The Gasserian ganglion is to be carefully exposed, and the three branches 

 of the fifth nerve shown. 



The contents of the jugular foramen are to be separated and learned. They 

 are the glosso-pharyngeal, pneumogastric, and spinal accessory nerves, occu- 

 pying the central compartment ; the inferior petrosal sinus, the anterior com- 

 partment; and the lateral sinus, the posterior compartment. 



The Middle Meningeal Artery. Figs. 6 and 10. 



This artery within the skull is found coming through 

 the foramen spinosum and grooving the inner surface of 

 the skull as it winds upward and backward. 



It divides into two principal branches, the anterior and 

 posterior meningeal. These between them supply the ante- 

 rior, lateral, and posterior areas of the skull and dura. 

 For the origin of the artery see page 121. 



The anterior, small, and posterior meningeal arteries 

 are very small, and will not repay any time expended upon 

 their dissection. The anterior are furnished by the ethmoi- 



